What's the advantage of a criminal sending me their seed phrase ?
Its a reverse scam technique. They first give you the private keys with some (fake) tokens in it but they require some gas fee to be transferred into your wallet, right? The moment you send few bnb or trx into that wallet for gas fee, they auto send it to the scammers' address (via a smart contract arranged).
If anyone shows you a btc balance and gives their keys especially on bsc/erc-20/trc-20 chains, its most likely a scam, dont get tricked.