Alpha-gal ( which is named for the molecule it affects, I think?) actually causes other problems beyond just inability to eat meat. I think it is technically true that you wouldn't be affected if you were the absolute perfect vegan, but in practice, nearly unavoidable cross-contamination in miniscule amounts can cause a severe reaction. For example, sugar can sometimes trigger it, as it is sometimes processed over animal bones. Or certain medicines, like anti-venom. Or many common painkillers, including formulations of Tylenol and Aleve, some vaccines, some cancer drugs...

Personally, I think it's quite scary, even for vegans.