Biden thinks (or at least says) that there are plenty of non-MAGA Republicans.
I think "MAGA Republicans" is a very hard term to nail down (not aimed at you, Dittohead, just my thoughts in general).
I don't think I was a "MAGA Republican" when Trump was in office. I reluctantly voted for him in 2016, and somewhat enthusiastically voted for him in 2020. I complained plenty about some of his decisions, so was not in the "Orange Man can do no wrong" camp. I never got into any of the MAGA hats, shirts, or other worshippy stuff while he was in office. I kinda thought that stuff was a little stupid.*
The first time I got anything MAGA related was when Biden et. al., started doing "Ultra MAGA". I bought the T-shirt the next day. It wasn't about Trump, but rather that I felt targeted simply because my Venn diagram and Trump's intersected in a few areas. It was an FU to people trying to make me into an extremist.
IMO, "MAGA Republican" today is a much larger and diverse camp than it was during Trump's presidency.
*ETA: JMO, but I've never been a fan of wearing shirts or hats for any candidate, not just Trump. Also yard signs, bumper stickers, etc. It's just not me. Not saying others shouldn't, just that I don't. I look at the "ultra MAGA" kind of how I look at Molon Labe.