I never seen an HMI application so I can't say.
It's just a term for software to operate machines using a industrial touch panel (which necessarily are much less sensitive than phones, since it is often covered in grime etc) Since scrolling is awkward you don't want a layout paradigm that has wide spacing and adds a scroller constantly.
And while in theory you can get html to layout very tightly with css for a defined browser with defined fonts installed, that usually beats any of the (portability, longevity) arguments for html, and then it is just a more difficult solution without benefits. Specially because these apps go for maintenance for long times, but not indefinitely (*)
That said, I deliver them mostly on Windows which is fairly stable GUI wise. I did have some breakage with Windows XP (with theming enabled) and Vista and later (always), that sometimes labels directly on a tform/tframe are not repainted for some reason. Putting a panel inbetween solved that.
Reading this thread, I remember why again
(*) many of our own machines are not connected to the net, so don't run windows update. Occasionally for revision purposes the customer moves them to an engineering area and connects them to the internet, against our express wishes, running updates and wreaking all kinds of havoc.