What counts for squadron leaderboard is the exploration rank progression. (The vast majority of it comes from data sales, of course.) However, I don't know how that works for crew: obviously they lower the credit payout when selling data, but do they lower the rank points as well? At what point is their cut applied?
You'd have to do some experiments to figure this out. Ideally, a non-Elite-explorer would sell data (with crew present) and note down how much percentage progression they got for how many Credits, then we'd compare that with known values.
However, doing it after you've reached Elite is also possible. 2 Cr of data will give the squadron 1 exploration leaderboard point. If for example you had your crew taking a 20% cut, then you could sell 10 million Cr worth of data, for which you'd get 8 million Cr, and see if the squadron got 5 million points or 4.
Unfortunately, I'm not currently in a position to do this now, although I am interested in the results.