Yes, this is very normal, and fully supported by Airbnb. Easy to link, and it doesn’t mean you are renting your house ‘AND’ a private room of course.
A large number of hosts run this arrangement, giving you flexibility to rent space as you need it. It’s not against policies, and it’s certainly not deceptive. Good you were able to help the host in this - always nice when we can support each other, and it can be confusing in this calendar sync area I know.
It seems however, that your misunderstanding comes from not being aware this is the exact same concept. Listing room A and Room B (separately) and a ‘Room A+B’ listing (together) is pretty common, even if the two rooms contains the same ‘one’ room - and so too for a whole house vs a room listing - it’s the same space, but you can’t rent both at the same time obviously!
It’s fully supported in the platform, and very normal. Millions of hosts would have this arrangement if they rent rooms - and certainly several I know, and the platform is designed to support this - linking multiple rooms to a ‘whole house’ listing.
A tip though - it’s always good to be curious if you don’t understand, and learn more - rather than appear misguided with a comment. I’m happy to explain and support other hosts in their journey - just as you like to do as well. But personal insults are not just unprofessional - they annoy other hosts. Let’s Keep focus on the hosting topics, and not harassing others. Nobody is interested in rude spam comments - so let’s keep bullying playground insults for the playground, and keep this a positive, supportive forum where we can discuss hosting tips.
My tip on managing calendars for room vs house is literally the same one you were ‘helping’ another host on recently - so that is good. Calendar syncing can be challenging with STR platforms for sure. We can help others though 