Another specific example would be something like an IRIG-B (DC) timecode decoder where you need to provide a PPS signal that's phase locked to the P0 rising edg

Another specific example would be something like an IRIG-B (DC) timecode decoder where you need to provide a PPS signal that's phase locked to the P0 rising edge or maybe even just display the time. This would be accomplished by implementing a state machine to lock on to the IRIG frame and essentially run a PLL to synchronize one of the local timers. Decoding the IRIG frame would require you to be able to catch every transition of the signal. With a good implementation, you can achieve PPS accuracies to within a few clock cycles (with it being deterministic too).