See above answer. It is very easy to confirm they've held the job they claim on the date range they claim. If they have held a software engineering role for 8 years without getting fired, they absolutely know how to loop over an array.

Ha! if only that were true...

Maybe at a real modern "software" company. But there are plenty of places where 50% of their so-called software engineers couldn't write a simple program from scratch.

In fact, as I think about the cases I've seen, it seems to get easier with senior "SWEs". They can exist going to meetings and delegating work until one day they forget themselves and apply at a company that actually expects SWEs to have a basic understanding of programming.

Reference checking almost always happens after the interviews. So no, the interviewer would not be expected to know this and should make an effort to confirm the person knows what they claim to know.

Reference checks and employment verification are different things.

Reference check is done after the interviews, you ask the candidate for references (past managers and coworkers) and call them up. That takes a fair amount of other people's time, so it only makes sense to do it after you're fairly certain you want to make an offer.

Employment verification is simply getting a statement from past employers that this person worked there from date to date and held these titles. That's quick and easy.