Amp "timing" ?

I was reading someone raving about the impeccable "timing" of their high-end amp this morning.  I have heard this term tossed around several times recently in my dive back into highish-end audio. 

Can someone please explain what is meant by this term?  Is it snake-oil or confirmation bias?  I just don't understand how a human  can hear  a timing difference of a soundwave unless it's a 2nd+ order reflection.  

Thoughts?