I think we have eventually arrived at some logicThere's no logical reason to have them all the same. They count different things, with different end conditions. It's only your personal taste that everything be aligned.
Count downs to zero have the advantage that they don't require any prior knowledge of how long they are counting to.
but Count downs upwards have the advantage that where the time can exceed the maximum they can go red and keep going, to show everyone how much 'overtime' has happened.
- a shot clock should count down (length could be 60 or 90, can't go over time)
- but YC and Game clocks should count up (as both cards and halves continue indefinitely until the next stoppage)
The reason YC counters often go down is likely that people forget that the card period continues until a stoppage and always lasts longer than 10min