reaper & sample accurate sync out?

Look at the Clock. Is that the time? 

I think that is all a function of your hardware interface and more particularly the quality of your master clock.

I think that makes sense if I follow you correctly 

As there is no 'clock' as such in a DAW it would either sync to the internal computer clock (default) or to an external clock such as a device or clock source brought into a studio or used at home such as a 'Big Ben'.