I did a bunch more research tonight to see what I could figure out. I do think that in most ways Alloderm/Cymetra and Acell's MatriStem are fairly similar and generally used for the same purposes. I did find a reference that I was unaware of before that indicates what you mentioned which is that Acell MatriStem does have some small amount of growth factors that Alloderm does not have. These factors can be released over time and may provide some additional benefit to the healing process. Something I found interesting is that now some dentists are using Alloderm with PRP and claim they are getting noticeably better results with things like gum surgery. I also saw references where some doctors use Acell with PRP for better results for hair growth for baldness. 

It seems that Houser might be saying something different now than he told me a while back. Hopefully he has seen some results that have made him more optimistic now. Leogeo, I hope the additional growth factors give you some benefit and improve your outcome. Best of luck.