[JRTJH]

Black tank "anti-siphon valve" looks can (and do) change regularly. As soon as a "RV Parts Supplier" finds a cheaper Chinese product (that still works/"sort of well") they market that new design to the RV industry. If it's 10 cents cheaper, it's a "tempting change" for any manufacturer. So, there's really no telling what you might find in two "identical RV models" or what we'll all see "as replacements" if we order a new valve or if we buy a new RV....

As for "water dripping from the back left of the trailer" it could mean a problem with the black tank flush system, it could be a defective tank dump valve gasket, a damaged tank, a water leak that "finally showed itself" or any number of other things. The only way you're going to know for sure where it came from is to crawl under your RV and do some inspecting. You'll probably find that it came from the black tank flush system nozzle connection (or a related PEX fitting), but then, it may well have come from a number of other related/unrelated places.

You didn't indicate "how" you were using the black tank flush system, so if you had the dump valve closed, is it possible you overfilled the black tank? If you weren't using a water pressure regulator, you "may have" (no definite yes) damaged the black flush line or nozzle. If you damaged the anti-siphon valve, then the leakage would most likely be under the sink and readily visible. Since you don't describe any water under the bathroom vanity, I'd think your anti-siphon valve is not damaged. Yes they are "fragile" but if it's not leaking water under the sink, it's probably not damaged.

As for shape, color or size, like "favorite teddy bears", the anti-siphon valve comes in all different "looks".....