What is the reasoning behind defining as current-dateTime() and current-time() as being "current at some time during the evaluation of a query or transformation"?

Saxon seems to follow the above and return the same value for each call to the function, even during transformations that can last several minutes (or hours or days).

It would be really useful if it returned the actual dateTime at the time of the call so you could implement a progress reporting feature in the transform - you could say how many records were processed in a given time and based on that suggest when the transform might finish.

The spec does say it's implementation dependent, so I wonder why it's fixed when people can do that themselves with a variable... if it returns the time when it's called then it opens up quite a few possibilities (especially where standalone transforms orchestrate the entire processing)