I think California is a bit unique in that a very large percentage of trailers going down the road are toyhaulers. Not to say other states don't have them by any means, my point bein they are commonplace in Ca. The water tank issue is a Non issue for the most part. Industry standard since mid 2000s on toyhaulers is minimum 100 gallons. My weekend warriors is 150 gallons. Plus 51 gallons of fuel.
I've had toyhaulers for 10 yrs. not a single issue or even thought given to towing full , half or empty. The tanks are low and designed correctly and I've never had an issue either way.
I'm aware of the baffle and water slosh issue but those are considerably larger tanks that sit considerably higher on the vehicle.
I'm sure some people dump whatever they don't use at their dry camping site but I prefer to leave water for the trip home. Especially towing back from havasu.
Kind of like lifted trucks and trailer. It's commonplace in California with no more problems then regular height trucks. It's completely normal here but it doesn't seem so in other states.