It doesn't. It just mess up what is displayed, because internally schedule dispatch store everything in Date + Tick. If you match the setting that the original game use (including wall clock offset), it should display everything nicely.
I do find having to adjust the setting irritating for each save game, so usually I adjust day length instead. I don't think it used to matter much until scheduled dispatch, where suddenly precise timetabling is more common.
A user deliberately setting different ticks per minute values for their different savegames is not a use-case which occurred to me at the time.
I for one just set it once to a reasonable value and then leave it.
In principle this sort of thing could become a company setting, but that does introduce somewhat of a backwards compatibility and user-unexpected behaviour issue.
I'm experiencing a confusing bug with routing restrictions.
As in the image, the signals are set up so that fast trains long reserve through the station, while slow trains behave as normal. However, when trains enter from the path signal at the top right, both fast and stopping trains long reserve. It could be that I did something stupid, but this happens with roughly 1 out of every 5 or so similar signal setups, so I think it's probably a bug.
I've attached the save file.
This is most likely because you have level crossings on the far side of the station before the signal with the routing restriction attached.
This will probably have caused the pathfinder to switch to next destination look-ahead before the signal is reached, as the destination has already been passed. This updates the current order for the purposes of pathfinding.
In most cases this is useful (for pathfinding) but it can be unintuitive in some cases.
Using a non-lookahead order for PBS action tests might work? I will investigate at some point.