BECO
BlackRock Future Climate and Sustainable Economy ETF
stock NYSE

Not just the first four letters. Yes, the first four letters are unique but the words in the BIP39 word list were chosen for easy recognition. Trimming them to four letters cancels that advantage.
Stamped "BUIL" looks very similar to stamped "BULL", stamped "PRES" looks very similar to stamped "FRES", stamped "BECO" looks very similar to stamped "RECO", stamped "PION" looks very similar to stamped "PICN", and so on. If, in ten years, your seed is invalid because a T looks like an I or an R looks like a P or an O looks like a C SOMEWHERE in your 24 word mnemonic, how long will it take you to figure out which of the 24 word fragments has a glitch?

Not just the first four letters. Yes, the first four letters are unique but the words in the BIP39 word list were chosen for easy recognition. Trimming them to four letters cancels that advantage.
Stamped "BUIL" looks very similar to stamped "BULL", stamped "PRES" looks very similar to stamped "FRES", stamped "BECO" looks very similar to stamped "RECO", stamped "PION" looks very similar to stamped "PICN", and so on. If, in ten years, your seed is invalid because a T looks like an I or an R looks like a P or an O looks like a C SOMEWHERE in your 24 word mnemonic, how long will it take you to figure out which of the 24 word fragments has a glitch?