[MicroBob]

I'm 37 and am not as quick a thinker as a lot of 2+2'ers nor do I have any of the AHK scripts but I can play 20 tables of full-ring NL on Stars reasonably easily.
Once I get to 22-24 tables it gets a bit messy for me.
But 18-20 tables of full-ring NL is a breeze.

Him taking too long can mean that he's just playing a lot of tables obviously. But when he finally saw the chat he responded and that kept him more focused to act on that table quicker.

15 seconds also sounds like the amount of time it takes before the warning-beep thing goes off for a player, right?
If he's ALWAYS acting exactly the same amount of time on every single action then I guess that is suspicious.

But when I hear "every single time" I usually take that to mean "most of the time, when I was noticing...but I wasn't looking at every single one of his actions on every single table."

None of this means that guy wasn't running a bot of course.
But I think the evidence is far from conclusive that he is...as all of the stuff that is supposedly so suspicios in the OP doesn't really sound too different from how a lot of people go about 20-tabling.