The real dark bit there is that if someone else posts something publicly, but your own stuff is "obscured" in some way, they may be able to (falsely) claim prio

The real dark bit there is that if someone else posts something publicly, but your own stuff is "obscured" in some way, they may be able to (falsely) claim prior art, as the original author. Amongst other things, hosting something on github is a public ledger of authorship.