No, the issue is not that they have different pH requirements. In fact, their cultural needs are the same. What has changed with these newer varieties is that the breeders are attempting to remedy some of the liabilities of the older varieties – in the case of these two species, that is splaying. Splaying describes when a plant’s stems get long and heavy and the whole plant kind of splits open, leaving a hole in the center. The breeders have created these two varieties you referenced to not flop or splay, and they do that by selecting for shorter internodes (the space between leaves), or a slower growth rate. Both of these lead to a denser, shorter, more compact plant, which might be slower-growing than the conventional varieties.