Honestly, on either point, I think there's an argument to be made.
The first being that Vraska directly had directions plugged into her head by Bolas means there's as likely a chance they took as granted that it included all necessary steps and they just skipped them because they ARE extraneous.
Even further argument, there's no telling how Bolas might have altered the place beyond sticking horns on everything, because it was NOT like it is now anyways.
I found the relevant passages in
Champion's Trial, I'll quote them so that everyone is on the same page:
Many of the empire's more powerful servants practiced a form of mental discipline that allowed them to project themselves into a phantom world. They called this place the meditation plane, and as the emperor was only now discovering, it was accessible only from Dominaria itself. [...] Bolas concentrated on the meditation plane, studying it. It was not a proper plane, but some sort of psychic construct, a dimensional annex connected to Dominaria. He could not planeswalk to it, but now that he had discovered it for himself, he could project his mind as easily as his subjects did. (pp. 290-91)
And the bit about Tetsuo managing to enter it physically:
Tetsuo slashed his soul-sword in a circle behind him. The gleaming blade left a blue-black circle of light in the air. Emperor Bolas lashed out with his gigantic paw, but Tetsuo dived through the circle and vanished even as his exit was obliterated by the great scaled limb. (p. 290)
Tetsuo appeared on the meditation plane. The means by which a person could physically travel to this plane had been lost for centuries, but with Ayesha's help and years of practice, Tetsuo had found it and put it to use. (pp. 291-92)
Then there is that one bit that might provide a way out for Creative if they choose to take it:
The realm of mind boiled and broke under blinding waves of light and pounding tides of mystical force. It would be months, perhaps years before the meditation plane would be fully restored, assuming it could ever be. (p. 301)
So, sure, Bolas could have altered it somehow, but that's guesswork and handwaving as long as it's not made explicit. Deciding what counts as a retcon is rarely an exact science and you always have to leave room for some handwaving, but there are limits. With what information we have right now, it's simply a crass contradiciton of everything that was established about it. It would have been no problem at all to write a paragraph from Bolas's perspective where he's pondering his plans while chilling on the meditation plane and where it's explained what he did to it. Besides, the Mending strengthened planar boundaries rather than weakening them, so it's even more unlikely that you can now planeswalk to a plane you couldn't 'walk to previously. If it's going to be addressed at all, it'll probably happen on Dominaria next year, but I'm not going to sit here and wait for an explanation I know Creative isn't interested in providing. If they do convincingly explain it away as an in-universe change, I can still remove it from the list.
And I'm going to disagree on the part where a proper portrayal of entering the plane would have been extraneous. If you give Vraska hoops to jump through anyway, why not the proper ones that should be there already? Besides, we're returning to Dominaria next year anyway, why not quickly bring it up now? Really, a proper use of established rules would have added to this story rather than distracted from it. It's completely beyond me why they would choose to alienate older fans who know about the meditation plane instead of just taking a moment to introduce everyone else to it and make sure they're on the same page. Being a storyline fan pretty much stopped being rewarding years ago.
Second, I'm not that upset about the gorgon alteration. It might buck against traditional depictions, but having it function equivalent to a dragon's breath is an acceptable change given the setting.
That doesn't make it any less of a retcon, though. Personally, I'm bothered tremendously. It just makes all races more similar and takes away any drawbacks of a gorgon's power. It completely alters what being a gorgon
means. Besides, it's a massive retcon that means several scenes from older stories don't make sense anymore. 'Xathrid Gorgon' in particular hinged on the fact that the guy manages to get himself petrified before the gorgon can take his eye out and sacrifice it to a demon. And how are they going to handle Ludmilla if she ever shows up again (okay, they probably threw her under the bus for good, but that's a bad thing in and of itself)? This is a textbook example of the messiest and most cancerous kind of retcon. Creative just has to understand that it's not always about what's convenient for them. They should have thought about that problem
before they decided to make a gorgon planeswalker.
What's more, the way gorgons supposedly work now is just counter-intuitive. New players or people unfamiliar with the storyline would expect gorgons to just petrify everyone all the time because that's the concept of Medusa most people are going to have in mind.