This is interesting, thanks. I've entered Doha on a <8 hour layover before, usually around 6pm connecting to a 2.30am departure. The first time was under the old visa-on-arrival and the second under the then newly introduced visa waiver. Didn't get any questions the first time round, but the second officer asked me twice where I was staying; I simply told him I had a connecting flight the next morning and was heading into Doha for dinner. He didn't seem too perturbed. I may choose my words more carefully next time.