Welcome, Hi-Potter, Yes that makes a very nice (a little expensive)installation, but you'd better put a switch in that W/P Extension Adapter.
Unless the wH came with the cord, I don't think that it can be connected this way. All bathroom recps require GFCI protection, but no receptacles are required at all in this bathroom.
On another note: That water heater and the added plumbing under the sink sure make it ADA ngerous place for any one in a wheelchair.
"Yes that makes a very nice (a little expensive)installation, but you'd better put a switch in that W/P Extension Adapter"
In a public place, ( such as this looks like)...I don't see any other way to install this. I'd wire this just like it was a "insta-hot" unit, which are almost always located directly under the sinks.
GFI or no GFI...I would never cord and plug this installation. How do you tamper proof a corded unit?
In regards to the "switch"....I've always treated these types of units similar to restroom hand dryers. If you have to service those, you'd be tagging them out at the panel. ( since you can not install a switch)
But as usual, I could be wrong regarding all of this...
These water heaters do in fact come with a cord attached. There was one installed at a former employer of mine and it came with the cord on it. While I don't know if it violates code at least it was plugged in to a GFCI outlet. Still kinda scared me though. Ian