some people are speculating that S tier TF players (like misaya) have known this for a while but credit to bischu (aka hitchu) for being the one that put me onto it
also if it doesn't seem to work for you the first issue I had was that sometimes it beats once right when I locked and I didn't count that, once I made sure to not miss the first beat I was able to consistently lock two gold cards in a row every time
also note: this is more of a proof of concept video for people who don't understand how/why this trick works, I may have missed some subtleties