Again, only by our standards for promotion. In Napoleonic navies this sort of thing was more the rule than the exception; until you made post captain seniority didn't matter.
Not really comparable, though, as it would take only three promotions to reach captain in the Napoleonic period, instead of seven. And though the percentage of captains inservice then might not be much different from a modern service, many of these were on half pay without assignment, whereas today they would have left the service or retired.
We already know that Starfleet doesn't worry about time-in-grade the way we do today. Riker doesn't really damage his career by remaining as Picard's XO long after he could have been promoted, and nobody thinks there's anything all that weird about the alternate Picard staying a lieutenant forever.
Rather preposterous arrangements which give no thought to the larger personnel management implications. The more that model is avoided the better.
Instantly going from cadet to captain is still excessive, of course. But here's how Thomas Cochrane (the model for Jack Aubrey in O'Brian's novels) did it.
1793: Joins RN as midshipman, aged 17
1795: made acting lieutenant
1796: passes lieutenant exam
1800: appointed to command a sloop
1801: promoted to post-captain.
So that's eight years from midshipman to full captain.
The personnel practices of the Royal Navy c. 1800 are probably not a very good comparison for Starfleet. The navy's policies reflected the class system of the time, when social background and political connections mattered more than ability. Cochrane had an enormous benefit in that he was born Lord Cochrane, heir to the Earl of Dundonald, and entered the navy at age five -- on paper -- when his navy captain uncle entered his name on his ship's roster. It is true that he had great ability, but officers like him or Nelson (whose uncle was Controller of the Navy) were more likely to have their abilities recognized than officers from a middle class background.
--Justin