The Amazon review does have a picture of the inside and it does the job for the 3 reviewers. And maybe it does need a pre inspection as suggested by one reviewer.
For an RV I would: Change the input and outputs to a 30A RV plug. Then use adapters to allow for 20/30/50A RV pedestal plugs.
The wiring looks small for a full 30A and one unit has a lower rating.
I'd disable the 220V output switch so that it can't be accidently switched to that output. As noted above it doesn't appear to be 120/240V compatible just 220V and the wiring/plugs confirm that.
However in terms of being in a CG with low voltage these units could be useful. And in places like Mexico with it's 127V standard (and often reported higher voltage) it would help.
I'm considering taking the rig to Puerto Penasco for the first time and others have noted over 130V.