I'm surprised that something like that would have got passed initial verification on something only two years old.
I suspect that for some, initial verification consists of checking the contents of the brown envelope. OK, that's a bit harsh - checking that whoever does it can fill in the paperwork well enough not to arouse suspicion.
FWIW, a few years ago my mother was looking at a new build. I was primed to pick up on the electrics and call the contractor out for fraud, and their scam for being useless. Some of the failings were "sort of understandable" (such as the cables in the kitchen not in a safe zone, because they'd left extra length for after the units were fitted, but the socket ended up several feet to one side), but others weren't (such as meter tails buried in the plaster and not RCD protected). Thankfully my mother decided that it wasn't going to be the right property for her. Nothing was "good" about that house - the electrics were "minimal", the plumbing was 'kin sh**e, it was designed to give her cold feet (solid concrete slab, insulated but not heated), and pretty well everything was "minimum the BRs allowed".
As it is, I'd already phoned the insurance company that was going to be providing the 10 year builders insurance and told them I had reservations about the stairs - 1/4" sag in some treads even after having been bodged underneath with random bits of timber ! I didn't think it a good idea leaving something that might mean ripping out the stairs and re-doiong them, along with all the re-decorating, till after she'd be moving in. Clearly my reservations were correct, it happened that shortly after that, my mother went to tell him she was pulling out (the house was supposed to have been ready at least a year earlier and still wasn't), and she called me to say that the vendor was in tears and saying that I'd caused him a lot of trouble.
And then there was a program on telly a year or two ago that looked at problems with some new builds. Examples included some built by one of the big outfits, who self-certify for BRs, and which had faults such as insulation still being in it's rolled up and bagged state just left in the loft - the builder had to take roofs off to fix that (sloping ceilings).
So no, never assume that because it's new and "signed off" that it isn't a load of sh**e - because some of it is a load of sh**e.
What would generally be the correct way to make sure the opening where the wire from the wall goes into the back of the socket?
And no-one's commented on the other fail there - it doesn't look like the cable has any protection as it passes through the cavity.