During discussions of another topic https://forums.ni.com/t5/LabVIEW/Starting-data-acquisition-from-combination-of-two-triggers/m-p/3891... I realized what the problem is.
As Kevin Price pointed out:
"As you have things, you're relying on the default "auto-start" property (settable with a DAQmx Read property node, but defaulting to True). In this mode, a call to DAQmx Read will make the task work through transitioning all the way into start and run mode. Because you have a finite task and you're asking to read the entire finite dataset all at once, the task will then auto-stop and revert all the way back to the state it was in before you called DAQmx Read. From memory, I believe this extra overhead may take as many as 10's of msec, during which time you might miss a trigger." When I added retriggerable, Start and Stop before and after For Loop, respectively, it was no delay anymore in Loop execution.
