If it was improperly set up, it won’t show at 100%, or anything unusual. The morph might also not be in the head section despite affecting the head, as the morph creator can put it wherever.
And someone dumb enough to set a morph to default at 100% is dumb enough to put it in a weird place.
why Daz allowed it to work that way is beyond me.
Because that's how DAZ3D does things.
No, I'm not joking, I'm being completely literal.
See, DAZ, as a company, is a paradox. On one side, they're perhaps one of the best 3D asset creators at this point, especially when it comes to pre-built base figures and characters, with props, environments and misc assets close enough to that... and, on the other hand, they have most of those assets in a proprietary format, that demands use of their software... a software that's unbalanced, unoptimized and unstable most of the times.
What's worse, is that DAZ Studio, the software suite, has the exact same core problems it had back at the 3.x version, nearly a decade ago. It's the main reason why Poser became as popular as it did between Poser 8 and Poser 11, becoming the tool of choice for anyone doing erotic art and animations.
The fact that Poser's current owner company, SmithMicro, pissed themselves while winning, only cemented the neglect Daz Studio suffered from.
Due to Smith Micro's inability to cut a deal with DAZ3D, and get Genesis 3, and Genesis 8, capable of working within Poser, it made the already problematic Daz Studio suite the only option. And, that monopoly status made any thought of actually fixing shit go down the drain.