Possible in-universe explanation: I would guess people suspect that barring emergencies double-wizards keep their abilities secret. So Susan can use her double-wizard abilities just that once when she really needs to. A double-wizard would get in trouble for using their abilities all the time just as a wizard would get in trouble if they used magic around Muggles all the time. Also, what Harry does is so weird that it doesn’t even fit what they think a double-wizard might do.
Probable actual explanation: Eliezer didn’t think of the double-wizard initially.
The obvious conclusion is that Harry is a triple wizard pretending to be only a double wizard pretending to be a wizard (who sometimes pretends to be a muggle). Twisted indeed are the minds and deeds of triple wizards.
Considering that Harry is being taught Legilimency behind the scenes, was given an invisibility cloak and time-turner, has lunch every week with Quirrel, researches the science of magic with Hermione, and probably a bunch of other things I can’t think of, I think it’s safe to say that he IS a double wizard.
Why has no one advanced the hypothesis that Harry is a double wizard?
Possible in-universe explanation: I would guess people suspect that barring emergencies double-wizards keep their abilities secret. So Susan can use her double-wizard abilities just that once when she really needs to. A double-wizard would get in trouble for using their abilities all the time just as a wizard would get in trouble if they used magic around Muggles all the time. Also, what Harry does is so weird that it doesn’t even fit what they think a double-wizard might do.
Probable actual explanation: Eliezer didn’t think of the double-wizard initially.
The obvious conclusion is that Harry is a triple wizard pretending to be only a double wizard pretending to be a wizard (who sometimes pretends to be a muggle). Twisted indeed are the minds and deeds of triple wizards.
Considering that Harry is being taught Legilimency behind the scenes, was given an invisibility cloak and time-turner, has lunch every week with Quirrel, researches the science of magic with Hermione, and probably a bunch of other things I can’t think of, I think it’s safe to say that he IS a double wizard.