True, though we have rather tolerant settings for fast respawn, I can hardly notice the difference (vanilla spawn doesn't bother me). Maybe that's why you didn't notice it before, Disco?
I think the way it works is by reducing the TF2 respawn wave times. Using vanilla respawn times you can have to wait up to 20 seconds to spawn depending on the wave timer and/or if a point has been capped (which I think can reset the timer again?)
The fast respawn should mean that you'll never wait longer than roughly 10-15 seconds before respawning. And that's including the kill cam which is 4 or 6 seconds.
I agree.
Vanilla respawns depend on how well your playing and what team your on. i.e. dustbowl, your on red and playing crap (negative kpd and dieing very quickly following your last spawn e.g hex as pyro

) your spawn time will easily reach 20 seconds. Don't believe it restarts on a cap though.... but I may be wrong.