If the shop has 100 bikes on sale, I wouldn't expect the employees to know every sprocket on every bike.
However, in general, I'd like to see detailed spec sheets on the bikes, so a person isn't sitting there trying to count sprocket teeth.
The employees should be familiar with major differences such as groupsets. 1x, 2x, 3x, etc. Or, if you ask them to show you a SRAM 1x bike, they should be able to find it reasonably quickly, or confirm whether they have one.
I am pretty good at finding general locations of items in stores that I'm familiar with. But, there are those occasional item, for example in a hardware store, that can be hard to classify, and I find it amazing that many employees are quite good at giving directions down to an aisle number (I tend to think about locations in store without memorizing aisles).