It happens all the time with pipe fitters !!
The guy doing the installation works to a drawing and spec!
To him it is just a pipe regardless of whether it will carry gas ,air or water!!
Why would he need to be corgi as he is installing to an engineers spec and has no say in the design!!
When completed some one comes around to test / purge and issue certificate!!
It certainly does Terry and it's still illegal, and as for working to an engineers spec it should be taken as indicative only, I could write a book on so called experts cookups