Many of the distinctions people use in talking about rpgs online are often modeled after D&D or colored by the experience of playing D&D, watching shows like Critical Role and the like. So, when people say "high fantasy" they actually think high-level post 3rd edition D&D and when they say "low fantasy", they actually think of low-level play in some OSR D&D retroclone.
And BRP games never fitted these categories very well. In Stormbringer your Melnibonean sorcerer could literally summon the Lords of Chaos upon the Earth, but a lowly Nadsorkorian beggar could still one-shot him with a lucky critical. Is this high fantasy? Of course it is - it's uber-fantastical. Is this the kind of high fantasy someone with a D&D mindset would expect? Surely not.