Fair correction. Never owned an HX One. That said, Line 6's website is a little misleading then:
https://line6.com/comparison/processors/
The One is explicitly listed as an "Amp & Effects Processor," whereas the Effects is the only Helix product in the "Effects Only" section.
And again, I understand that this is the underlying design intent of the HX Effects. The question I'm trying to ask is whether or not this is an arbitrary limitation of the software. As an HX Effects owner, it would be hugely helpful to have those additional models as a value-add/back pocket gig insurance. It's still strange that the HX Stomp is, from a DSP perspective at least, the more flexible option.