What was pictured is technically a "flexible applance connector" listed to ANSI Z21.24. The basic application here is acceptable to the flex mfr. as long as it is not exposed where it could be expected to get damaged. It depends on what is going on to the side of that WH where the folding chair is. Personally, I would have run 1/2" CSST from the shutoff to the sediment trap/ valve.

__________________
disgusted with some people on this forum. Out of here!