No, phasing happens when two signals are of the same frequency therefore canceling out vital sounds that would've otherwise enhanced the sound, has nothing to do with timing. If you was recording guitar in one room and drums next door at the sametime and the drummer is banging so hard that his sound leaks into the guitar mic then phase will occur dumbing down the drums because the waveforms are the same.
Sorry but this is not entirely true. To anyone that doesn't know, or thinks they know, take this as a moment to educate yourself on what exactly is happening.
Two waves, of the exact same frequency, played at the EXACT same time, will sum, thereby becoming louder..
Two waves, of the exact same frequency, played at the different times, could cancel each other out at times, but it depends solely on the timing and how offset the waves are from each other.
This is physics, there's no way around it.
It actually IS all about timing, because as soon as they start playing at different times, the samples of the wave might interact in such as a way as to cancel each other out. If you have two waves, same frequency, and play them at the same time, they will double in loudness. If you play them such that the peaks of one wave coincide with the valleys of the other wave, then they will cancel.
It is dependent on lots of things, but timing is a HUGE part of it.
Also your example about drums leaking into the guitar mic is not entirely accurate, and can't even be summed up that simply. Depending on the mics used, mic placement, air in the room, etc etc, it could do any number of things, but definitely not simply 'dumbing down the drums'. If anything, it will make the drums seem fuller as they are coming in on more tracks. In this case, it comes once again all down to timing. If the recordings of the guitar mic and the drums are played at exactly the same time, it will likely make the drums louder (by a tiny tiny amount). If however there is a small delay (delay in the sample range...sub-milliseconds), it could produce phasing. But yea, in that case, it's actually all about timing. The 'dumbing down' you hear is because the drum sound is hitting the drum mics and the guitar mics at different times, and the timing offset causes phase cancellation.
You can do this experiment yourself in your daw.
Set up a test oscillator ringing at 220 hz on track1.
Set up another test oscillator ringing at 220 hz on track2.
Make your DAW output mono (this is very important).
Play both, and you will notice you still here the wave perfectly fine, maybe a little loud, maybe even distorted.
If you adjust the phase of the oscillator, start doing it, you will notice the main output tone start to get quieter.
If you cannot adjust the phase of the oscillator, you can use a sample delay....but it has to be a true sample delay where you can adjust the delay rate by 1 sample at a time.
If you have two oscillators at 220hz, playing at the exact same time, and you delay one by 110 samples, they should completely cancel out.
Of course, all this depends on the concept of sample accuracy...and if your daw, or gear (like the mpc 5000), cannot do sample accurate operations, then it's not going to work.