Regardless of the unicode issue (some trademark lawyers are going to make a lot of money from this one day), its not more accessible at all. It hides any information behind prior knowledge about the fedi-use of the symbol. It's even very hard to look it up, if you see in print or on a device you are not controlling so you can't copy-paste the symbol for lookup.
You know all those icons because someone, some industry or some culture imposed it to you. Nothing is self-evident. We are constantly learning new symbols to be able to share graphic languages with other persons or interfaces.
The rationale for having symbols I feel is so self-evident it shouldn't need any explanation. You know the save icon, you know the power button, you know the Twitter, well, X logo. You probably know the 'share' icon. I don't know if anyone's going to buy that it's bad to have a simple universal icon closely associated with a specific thing that we want widely known. And Unicode has an advantage over images of being, in a sense, more universal and more accessible.