I've never personally heard the dark forest scenario as requiring ftl tech,

FTL is the only thing that makes it applicable to game theory. If there is no import to respond instantly, then there is no imperative to respond.

The query is dependent on the hypothetical that the instant someone spots you in the dark Forrest they have an option of removing you from the game unless you remove them first.

making that a requirement seems to make the entire premise moot as it requires throwing a pretty fundamental part of physics out to even contemplate.

So does going to war with an alien race, or even finding another sentient race? How are you supposing these aliens are finding every sentient race in the galaxy if they can't push a search signal faster than an electron? It would take thousands of years for a signal to travel to the closest potential suitable planet, let alone every suitable planet.

The theory itself requires a suspense in disbelief, as do any that pertain to encounters of the third kind. I would say that the limitations in physics that prevent the possibility of FTL are of the same order and magnitude that prevent us from contacting aliens.