InDesign v 19.0 - Publish Online
I welcomed the fairly new 'Hide Spread' option, which is long overdue. But unless this is a bug, I am astonished that the hide spread feature does not work when you use the Adobe Publish Online option!?
I think the initial message said the hidden pages will be excluded when exporting (to PDF I presume), but I assumed it would also work when using the Publish Online option!
But my experience publishing online just now shows me the hidden pages are always included. I changed paste board set-up to 'Digital Publishing' in case that was needed (made no difference), and checked the preferences in case there was a specific option to take up (there wasn't).
Frustratingly a search of Adobe help and Google did not reveal whether this feature should work in Publish Online, or whether it did not.

It doesn't sound like a stretch to have that hide spread feature working on Publish Online, and it just seems like an error or massive oversight for it not to be included or referenced.