Well Chuck I have never flown seaplanes but I have many thousands of NM under sail, solo, in the open sea. I can't imagine ANY one could adequately instruct on seaplanes after just 7 hours total. They would still be coming to terms with the whole new deal themselves. Even 50 hours sounds a bit light on - maybe OK for lakes and other pussy ponds?
But I take your point - too much value seems to be placed on a Flight Instructor rating being the font of all knowledge.
Here in Oz, CASA just set up a specialist department to periodically examine all the ATOs (Approved Testing Officers) in the industry. Which means everyone from your local club CFI through to the Head of Flight Operations in a large airline. The one mandatory qualification that CASA required for the job was a Grade One Flight Instructor Rating. Not previous airline check and training experience for the airline supervision, tho' obviously that would help. Had to have the Grade One, no matter what.
Had I any real interest in such a job, I would be real p!ssed off at being excluded.
Setting the base standard on a qualification which can be gained entirely in light single engine aeroplanes and which has not evolved much in 50 years does not augur well for a rational approach to modern demands for the MPL etc.