Didn't notice any changes regarding this, i have a coaster running in test mode (during transition of the Winter Update) operating with 5 RVs and it didn't change its timing behaviour so i guess the issue not related to the update? (It's set to "min. Departure Time" rules.)
Do you have the "Don't block station" checkbox active? if so, turn it off. Also uncheck both min. and max. loading time AND set capacity to ANY LOAD.
In testing mode, it should work if you unchecked all the aforementioned ticker boxes.
However, I noticed is the timing setting is sometimes not exactly what you set it to .
(seems to somehow round up or down the numbers (i.e. you set it to 17, it departs after 15 secs., you set it to 18 and it departs after 20secs.))
Then again, this in particular might be fps related.
Also once the coaster/track ride is in operation, the timing (especially at shorter departure settings) might be influenced by how quick the guests leave the platform (independent of guests entering the ride, if the interval setting is set too short the car will just leave empty)