Every major company has company wide inventory. They have specialist buyers for different departments.

They either know, or have purposefully arranged things so the people who know enough aren't burdened with knowing everything. Neither is acceptable.

They could be idiots who don't know what they're doing, but then they wouldn't still be in business.

I returned cheap electronics to a UK store recently, it was very clear the entire batch didn't work, indeed it was probably why they were on offer. People will say "oh it was only a couple of quid, won't bother taking it back". Still on sale. I wouldn't be surprised if they hadn't reshelved the non-working ones I returned.