Yeah. I tend to hate hydros, since I do my own visuals but have to drive an hour for a (highly entertaining, I will admit) hydro. But if you think about it, the cost of hydros is actually less per year than the price of visuals these days, if we figure $40 for a hydro and $10 for a visual. So from your point of view, throwing away 1/5th or so of a hydro, to gain 1/2 of a visual, is not unreasonable, when you add in the convenience of not having to leave the tank again. So you have done nothing stupid.
So if you did it on the basis of that math, then you have done nothing stupid. But if you did it because the dive ship convinced you that it was somehow necessary to have the hydro schedule perfectly in synch with the visual statement, then you have been suckered, but a shop that hasn't a clue about the actual rules.
Personally, I did it on the math and hassle factor. The nearest hydro test facility is 2 hours away, so that equals 8 hours of driving(4 hours round trip to leave the tanks, another round trip to collect)$80 worth of deisel, yada, yada. I convinced myself that getting the hydro and visual in sync was a good idea.