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.
PS: If they give you a seed in the form of recovery file, it most likely contains malware/trojan, delete them immediately!
Seems like its very similar to Macro viruses isn't it? Micro virus embed themselves in word-processing documents (like MS word) that are mostly attached with an email. When the victim clicks the file, the micro virus code is executed.
The basic idea behind every modern virus/malware is to trick the victim to do a very simple mistake that results in execution of the virus program (in this case its execution of smart contract when victim send token in wallet).
By just reading such replies one can surely save himself from scams. Your reply is worth sharing.