>Is this true and can someone vouch for this?
Yes, and yes.
> There is also a few hints that TBHs won't make as much honey as they could and that empty bars must be added between the brood nest and the honey storage area.
I've never worried about that, but you could put bars there, I guess. I don't see that they make less honey, but you have to harvest more often to get the same amount of honey.