With the Lightbringers, Earth Goddesses, Prosopaedia, and Glorantha Sourcebook out – and with the Mythology book coming out next month and the Dragon Pass and Sartar books next year – it should go without saying that we have more material out on Dragon Pass, its myths and cults, and so on than all the older material combined. This is truly a golden age of RQ.
It also should go without saying that it should be utterly unnecessary to consult out of print materials developed for another game engine in order to use the new RQ materials. So if you recall something in Storm Tribe (a supplement for the Hero Wars engine from over 20 years ago) or from the Book of Heortling Mythology (a compilation of stories that was put together as a reference FOR Greg almost 20 years ago) that is absent from the new materials, that is likely intentional. You can certainly comment on the change, complain about the change, or just ask about it. You can even use it in Your Glorantha if you want.
But please don’t treat that material as background canon here. It is certainly not canonical as far as the writers and developers at Chaosium are concerned. Nor is it accessible to the large numbers (probably the majority) of people who are here because of RuneQuest.