I had a shared drive on virtualbox where I had the problem of the clocks not being in sync. There is also the fact that some other tools aren't necessarily well behaved and will dirty files, causing spurious rebuilds.
For the most part though, you're right!
I'd think the far more usual case is each dev has a copy of the code on his/her own machine, and another copy is on a build/test machine. There won't be any timestamp issues there.
Make is like a lot of tools, it's simple and works well, up to a point. If your project complexity exceeds its abilities, you likely can afford something more sophisticated, since you probably have dozens or hundreds of developers anyway.