I think a lot of online information is dated, much like you see nowadaways with caresheets that are sub-par for herps. Cockroaches are pretty forgiving to husbandry errors and can thrive under a variety of types of care. One method may seem to work fine as the insects are reproducing and thriving, but that isn't to say some other methods aren't better for increasing reproductive fitness and vitality (as we are finding out with improved care practices).
The nutritional similarity is probably a result of similar cockroach morphology and diet. Blaptica dubia and G. portentosa are probably pretty distant relatives in Blaberidae (the prior from New World regions and the latter from the Old World). Their actual life histories and physiology may vary quite a bit despite both being cockroaches.
Oh, and I almost forgot to mention...congrats on the roaches timscape! You'll love em' = )