You can already quit if you don't like the room, you just have to do it before entering the lobby during matchmaking. Simply suspending gts (by choosing to trim a video clip for example) will exit you from matchmaking without any point loss.
Only once you have entered the lobby, you will have wagered your DR points and suffer -5 SR for a disconnect or exit.
And if you disconnect after crossing the finish before re-entering the lobby you still lose 5 SR and are counted as DNF, i.e. lose tons of DR. However getting disconnected or quitting usually preserves your clean streak. So many things don't make sense!
I tried race B this morning, got SR Down from a draft bumper, the same bumper bumped me off in the hairpin, didn't get a penalty. So much for that. BS penalties on Tokyo, or getting bumped out of the way on Yamigawa, or fall asleep on Suzuka, take your pick!
Suzuka actually went quite well for me last night, 11 positions gained. No clean race bonus though since draft bumping happens there as well. Race A and B are too short, yet race C, yawn fest in the last couple laps. This car is so slow I'm thinking can I brake yet for the hairpin, how about now, nope still too soon