Charlest -
The Hellraiser may be a hybrid solid/pearl, I'm not certain ... the official description is "Class 5 Reactive".
That would explain why it would start up sooner according to Brandon.
Pardon my bluntness but, no, it wouldn't.
What would explain it is the strength of the coverstock. If they were the exact same family of resins, it would explain it, but you can't say that in this case. (We don't know that DV8 uses the same resins or even the same resin supplier than Brunswick does.) All one can see is that with similar core and numbers, the HR handles more oil than the Ulti-Max.
In general, solids are stronger than their equivalent pearl and solid/pearl combos are earlier and stronger than their pearls. BUT there are pearls that are stronger than some solids. So it's the actual strength of the coverstock that makes the difference.
That said, don't be too hasty to dismiss the HR or the HR family. The reaction I've seen so far from people using them tend towards an fairly flippy ball reaction. With the right drilling, and the right delivery/release, Hell Raisers, and Revenges can both handle a good deal of oil and have a pretty strong backend. If you're playing more on medium oil than medium-heavy to heavy oil and want that flippy backend, the Ulti-Max is probably more than sufficient, when drilled correctly and for your release.
Good luck..