constaint timing and ouput

I would actually argue Tsu/Th is the "weird" definition, although expect many will disagree. Tsu/Th describe when the data must be valid around the clock, but they both have the same sign and it's the name that tells you which direction its talking about. For example, if the numbers for a device were +3 and +2, you have no idea which is Tsu and which is Th. On the other hand, an input delay of -2 to +3 is a range and you know which one is the min and which one is the max. It's only one number, input delay, and it's given a range. I believe that would be the more normal way to describe something. (Imagine a thermometer where numbers above 0 and below 0 were both positive, and they needed a qualifying name to know which one you meant).

It is weird though, in that most engineers have had years of Tsu/Th pushed onto them to the point it became second nature, and now the constraints don't match that convention.

That being said, I agree with your write-up and realized I'm arguing over what could be described as "weird", so nevermind, I'm just distracting myself from doing real work. : )