I agree, doubtful that's a Japanese. Legs are too long(even for the long-leg version) and lack of tail. They;re a breed with very prominent tails...
If you happen to be looking for chicks again, put them on a shelf or something to make their leg length more obvious. Their legs are short right from hatch.
Pick the ones with really short legs if you like the 'no leg' look.
The short leg is lethal if pure(they die before hatching- no worries about chicks dying post-hatching), as a result it is necessary to breed short leg with 'long leg'. That will be why you might see variations. Even so, the 'long legs' are noticeably shorter than on regular chicks.
Definitely good to know! I have two that were said to be those, I wanted the four Golden Sebright and my (three year old) son insisted on the yellow pair. It was at TSC so I took it with a grain of salt, ha! My other six are Old English Game Bantams; these two I now have no clue. Long clean legs on both, I'm guessing at him being a cockerel since her comb is much less noticeable and not at all pink... Now to find out what he is!