I think the frequency of high CV cap you're seeing is just local statistical variation. It's kind of a good place to hang, if you're in a fighter. If there's no traffic, you can just meander and climb a bit. You've always got the friendly puffy as a heads-up warning - and as a place to run if you get damaged, You've got the radar, and you've got the bait. Usually, the bombers come in low but the fighters often have some alt, especially if they're covering for fighters that are heavy down on the deck. The main reason I'll climb over a CV is for them - intercepting bombers is of secondary import since they're usually thrown into the meat grinder a bit more hurriedly.
Regardless, I think you give too much credit to the typical CV barnacle. THere's no telling what's coming in. I frequently see heavies down low. Besides, G4M is listed in wikipedia as having over 1800 ft/min - TU2 only 1600... I recognize that we've been arguing a bit over the weight and that this last will affect the induced drag (thus affecting climb) but these two should be in the same ballpark. Thus, if Betty didn't change it, why would the Tupolev? Granted, I see the latter a little more, but neither are as common as, eg, an F4U. That's what I'm spiralling up for...