Yep, white lies. The underlying rationale is that kids do throw up in pools and you don't want to get into a public argument with a kid about how they're not going to throw up, can they go in pretty please.
It's like the thing about getting arrested for turning on the lights inside a moving car. No, you won't get arrested, but the reflection on the windshield can be annoying, and getting distracted by kids going ham on flicking the lights on and off is obviously dangerous.
As a kid, I always wanted to go swimming (swimming pool or sea) as soon as I finished eating. My parents told me not to because of the cramps. "You must wait an hour before swimming".
It wasn't about throwing up and as an adult I finally understand it: they wanted to have a chat at the table after eating, take it slowly, maybe they were a bit drowsy. What they didn't want to do was to look after kids doing potentially dangerous activities such as swimming. So that hour of waiting? A period of grace for them to enjoy their meal and maybe rest for a short while.
Nah, it's definitely the hygiene thing. Pools often forbid food and drinks at the deck for the same reason: if someone dirties the pool water, they basically need to close off the whole pool and recycle the pool water for a few hours, which is super inconvenient for all parties involved (and obviously embarrassing for the parents of the kid who made the mess). You'd be surprised at how often these things happen.
In British Columbia, Canada, the BC Motor Vehicle Act mentions interior lamps in connection with larger passenger vehicles. In addition to requiring that they have them, it has this requirement that they be on while driving at night:
Interior lamp
10.20 (1) A commercial passenger vehicle shall be equipped with a
lamp or lamps within the vehicle so arranged to illuminate
the aisle of the vehicle to the rear of the driver.
(2) A person driving a commercial pass enger vehicle having a
seating capacity including the driver of more than 12 occupants
shall insure that the light or lights referred to in subsection
(1) are illuminated at all times that passengers are being
carried between sunset and sunrise.
AFAIK, that's meant for buses, and it's the same rationale as airplane floor lights (i.e. illumination is necessary to avoid falls from tripping in the dark, e.g. if the passenger is going to the toilet, which some buses have).
We had a child swim in our pool immediately after eating and she threw up. Probably where that one came from. Kind of like how it is bad luck to open an umbrella inside. It's not bad luck, but somebody might get poked in the eye.
It's like the thing about getting arrested for turning on the lights inside a moving car. No, you won't get arrested, but the reflection on the windshield can be annoying, and getting distracted by kids going ham on flicking the lights on and off is obviously dangerous.
See also, school "permanent records".