A good engineer has better dealflow than VCs. He can cherry pick companies backed by top VCs, within those he can pick the ones with the best engineering teams, for example.
I didn't mean that you should expect to double the salary for any given job stint. If you consider time horizon of, say 10 years, multiple jobs, 2x salary is quite a reasonable expectation.
If cherry picking worked, VCs wouldn't invest in the "not cherries". Actually, cherry picking does work, but the cherries aren't clear until after all of the big engineer stock grants are gone. VCs get to cut their losses and double-down on their wins. Engineers don't.
Even if engineers averaged as much gain as VCs, the distribution will be different. The typical VC would be close to the average because they get to make 10-20 bets/year while an engineer gets to make <1 bet/year. As a result while the typical engineer would be far below average return. (Yes, a small fraction of the engineers would be ahead, but ...)
I didn't mean that you should expect to double the salary for any given job stint. If you consider time horizon of, say 10 years, multiple jobs, 2x salary is quite a reasonable expectation.