I don't think this is true. GS grades are capped by the compensation of Level IV of the Executive Schedule (sometimes with locality pay they would exceed that and so they get capped), which is roughly the same as Congress salary, but definitely SES pay tops out a good 25k above that.
Grow up in the DC area and even if you never work for the Gov't directly you just absorb this information out of the air.
Exceptions are made for federally-employed physicians, which is the only reason the military is able to have its own doctors. They could easily do the same industry gap compensation bonus on top of schedule for engineers if the non-government market gets to be similar to the physician market.
Well, but Executive Schedule people are essentially all political appointees, not individual contributors. This is the several hundred people who get appointed by the President- most of them requiring Senate approval- and come in to be the Deputy Assistant Secretary of Defense for Reserve Affairs or whatever. This is not the Civil Service but the political appointees who sit on top of them and cycle out regularly back to think-tanks or industry jobs when their party loses an election.
SES is not political appointees. SES are career executives, and generally serve through many administrations. Political appointees are usually 'Secretaries' and that ilk, which may be 'SES' equivalent, non-career/competitive appointments, but are not Career SES.
There are TONS of SES folks below the appointee level.
