They should sign an ethereum address to reduce ambiguity
(Any crypto asset address is fine, even PGP is good enough for this but PGP had 25 years to make that user friendly and common but failed, and cryptocurrencies made signing software more prevalent and uniform wayyyyy faster)
However, there's still some very good programs with good UX making use of PGP (for example delta.chat), and to this day no cryptomoney scam wallet has ever been as useful as PGP has over the years.
this algorithm has failed to proliferate outside of thin security conscious niches for an entire generation of internet users, and has been leapfrogged.