Skips as in... The game doesn't give you an opportunity to put a password that day? For me Thanatos still guides Dave to the vault the same way of the other routes
You can still use the password on Tyson's route for day 17. The investigation will happen and you get the prompt to enter a password like would happen with any other route. You can get the CG and everything.
The difference is, when the other routes shift into F or G at the end of day 19, Tyson's won't. By being on his route, even if you get the password wrong, Dave will stop anything bad from happening naturally through the story. You're pretty much dealing with the problem directly since he's your partner whereas you ignore him on the other routes. Affection level doesn't matter either, that has no impact on the main story (so be nice to him).
Really all it should take to be on path F or G is not use the password on day 17 and be on anyone but Tyson's route. You're technically on F/G the moment the password isn't entered, but the game will show as A/B until day 20. Since, ya know, Dave doesn't find out until then that he's on a bad timeline.