HBG are most often declared to revert back to GSF. This is impossible from a purely scientific standpoint, but in a practical, real world scenario GSF is probably a good a description as any.
I have wondered about whether this is one of those "it depends" scenarios. What if you have a few HBG in a pond full of BG?
In my opinion, the HBG would disappear over time.
Spark---I don't want to hijack this thread, so if you know of a good link this is discussed, please refer me to it.
If the HBG eventual revert back to "mostly" a GSF characteristic, would they not then be breeding with the BG and create a whole new round of HBG?