I used to think and understand phase as delay in a sense but have come to understand that delay is not quite exactly the same thing as adjusting phase. Yes, by adjusting phase you will "match up" two overlapping sources in the crossover region. However, you may be as much as a full wavelength or more BEHIND in timing. So the impulse response and initial attack will be blurred.
That said, I don't understand why many of these EQ and sub management systems that allow you to adjust from your seat remotely do not have a continuously adjustable phase option to adjust from there as well. Nor do the auto EQ room correction devices seem to adjust phase automatically...