Is the Shimano UN55 bottom bracket in 68x122.5 and 68x127.5 sizes JIS square taper? On one online sales site there's a drop-down widget showing various sizes of the Shimano UN55.  "JIS spindle" appears as a bullet-point next to someone of the size choices but not all of them, hence my question:

Is the Shimano UN55 bottom bracket in 68x122.5 and 68x127.5 sizes JIS square taper?

A technical document on the Shimano website didn't resolve my doubts since it doesn't address the spindle standard, and it doesn't mention the 122.5 and 127.5 lengths anywhere, and it shows this BB as available with either English or Italian threads, so who knows if the spindle shape changes too?

Many online vendors include generic pictures with their BB listings and often have incomplete descriptions, so that the inexperienced customer (like me) is often in doubt.  For example, I just bought a BB online that had 1.37 stamped on the body in the accompanying picture which turned out not to be 1.37 at all. It had 36mm OD cup thread, not 35mm (1.37).
It is JIS.

Shimano doesn't have separate Italian taper cranks, and it does not make sense to them to make BBs that do not fit their other products. Italian taper has been practically obsoleted since Campagnolo switched to two piece cranksets in the 2000s. If you manage to find one now from a competent vendor, it will be clearly marked as one.

Regarding your experience buying online, it does not sound like the vendor did know what they were doing.