I have noticed this with PT tutorials as well. I always wondered because it seems to be that the clips are split into musical phrases, rather than just chunks of the song like "chorus" etc. I could understand if the phrases had been punched in one at a time, but I'm guessing it's more likely that the parts were recorded in full and then split into phrases manually. I was watching one with a wah-wah guitar part split into phrases and I thought there's no way they were punched in separately.
I'm not sure I buy the disc saving explanation, seems like a pretty weak effort/reward trade off. Personally I've always wondered if some people just like to have their set out as split clips so that they have an instant overview of which instruments are playing when. If every track is one long clip, this is harder to see at a glance.
Did you notice if any of the clips were from VSTi's? If so then that would be significant since you know they would have bounced to one long clip and then split it manually. Unless of course they bounced little sections at a time with different synth settings to save having to automate it (I do that myself sometimes).