Huh, that's news to me. I had to do some googling and the only one I could find was by Phalicity which seems to be from a Meta employee who left and made it into a company (a la Statsig, or to some extent Graphite)

Seems that company shutdown though a while ago and it got forked into Phorge, but either way I assume there's some divergence from what's internal at this point.

Still I'll look into it, it does look neat and might suit my preferences still. Thanks for the headsup :)