Dictionary: is PWM precision the same of PWM resolution?
This is the way I've seen it defined:

Precision would be the amount of PWM you could deliver, usually in units of percent. 

Resolution is what the timer can deliver in 1/2^(n-1) fractions of the window frequency

I have not seen relative resolution, but this would indicate that one pulse is different from the next and by how much.

But precision makes up for an easy way to think of error, but hides what is really going on inside the 

There are a few things to take note of, there are rise and fall times and dead time to start a new cycle. There is also potentially clock error or jitter that could make each cycle repeatable only in X amount of time frame (like 1 ns)  All of these contribute to error.

Some very small pulses are not achievable with a high resolution PWM driver because even though the timer is capable of delivering a 32-bit time, if you only want 1 32-bit count and the window time was fast enough, the pulse would rise and fall before it got to the full voltage.