Snaily and Squishy_(artist) are not the same artist, Snaily claims that they don't personally know Squighy but odd enough their art style are both similar but not the same person. They also claimed and confirmed they were unaware at first that the name Squishy_snail in general already exists. So no, they heavily stated they didn't know the name already exist plus they aren't trying nor pretending to be Squishy.

IF they are, it be obvious they'll steal Squishy's ocs and stuff and ofc stealing art, now that's stealing and impersonating.
Keep in mind, the name squishy_snail(in general) is not copyrighted, I think anyone can name themselves that with numbers or whatever. I seen the names "squishy_snail" usernames on twitter, and instagram. Not everyone's username is unque, keep that in mind.