yeah....I read that somebody had crashed their Mini 5 with a Mini 3 pro Plus battery when the pilot ignored under-current warnings while in Sport ModeDJI do NOT recommend using Mini 3/4 Pro batteries in a Mini 5 Pro. Current draws are higher with the Mini 5 Pro. There has been at least one report of a Mini 5 Pro falling out the sky when using a Mini 3 Pro battery.
They might fit physically but are not electrically compatible. A really poor design decision!