IMHO the only question that requires appeal to data is the claim that most loops at the end of triple-triple combinations are severely pre-rotated (which may or may not get caught), more so than for solo triple loops.
The rule in question is the Zayak rule, and that's been in effect for years. What had kept the solo 3Lo in programs for so long is that under 6.0, a judge could decide to give a lower technical score to a skater who left out any of the standard five, because s/he felt that a skater should be able to at least one of each, something that many on this board and FSU have argued should at least get bonus points under CoP.
There was never a rule to say that a skater couldn't substitute a solo 3F for a solo 3Lo, but how often did you see this happen under 6.0, unless, perhaps, when a skater was injured? Would Kwan have beaten Koster in the Moscow LP under 6.0 had she left out the solo 3Lo? (Under 6.0, that was a full placement, not .69.) Liashenko actually won some events under CoP when she left out the 3Lo that had plagued her. Would Sarah Meier, Dan Fang, Valentina Marchei, Gwendoline Didier, Aki Sawada, and Anastasia Gizmadetdinova not have attempted a loop of any kind under 6.0, when they -- half the field -- did just that at TEB? Glebova left out a flip attempt, and Pavuk and Leung had only double loops in combination. Asada has a 3A, but she doesn't have a 3T or a 3S. That leaves only the silver and bronze medallists, Meissner and Wagner, to have landed at least one of all five standard triples. Although in 6.0 world, Asada's ratified 3/3 and 3A would have trumped all. (Ironically, it was her 2Lo at the end of the 3/2/2 that was downgraded, but there's not much to lose from a 1.5 base mark

)
The rules haven't made the solo 3Lo an endangered species; a combination of
incentives and the elimination of an inconsistent and unwritten rule have. What CoP has allowed is for a skater to substitute another jump for a solo 3Lo, and more skaters have taken advantage of this than the only two performing the 3Lo in combination, Asada and Ando. (And Asada substituted solo 3Lo for solo 3Lu at TEB, when she added the 3A, although she doesn't have a 3T or 3S.) Look at the young French skater in TEB: She attempted 3Lz and 3F in both programs, and had all but one ratified, but not a loop, triple or double, in sight.