Also, I want to reiterate that it's not just about consistent reverb either.
For instance, if you want to process a sound you have that already loops well by say, adding eq to it and then simply render it out again.
Well.. If you try this you'll get a "click"/glitch at the start/end of the loop. (try it)
The reason for this is that a lot of effects "slant" the frequency response over time. For instance a low shelf eq will progressively make the low frequencies out of time with the higher frequencies. (look at the phase graph in reaEq to see what I mean.
Now, when you try to reloop this, unless it's the second pass you render, the end and start will have gaps in the frequency range that get chopped off.
Hard to explain fully but the below kind of does
/----/ ends look like this frequency wise.
And we are going to chop them straight like this |----|
And what you actually need is the delayed high at the end that is chopped off to be put at the start of the loop to make it whole again.
Without diagrams hard to explain but this is a massive pain for game audio and 2nd pass fixes it.