What about getting 5 perks instead of 10 for killing several low ENY planes with a P-51D? Still sound like ENY is a non-issue?
ENY has two purposes. To "handicap" the high numbers side in the war, and to encourage people to fly rides which can do less by offering them more perks. You can't really base it on anything *but* plane capability.
And lets look at the problem in reverse. You will now get more points for killing P-51s with La7s-a plane which owns the P-51D in every performance metric at the most typical MA combat alts-than you will get for the reverse. It was perverse enough enough when killing an La7 with a N-Jug and killing an N-Jug with an La7 earned you the same points.
The P-51D is just not good enough to be a 5 ENY plane in the low-alt MAs. Its performance doesn't justify it, nor does its k/d.
Yes, earing perks in sub ENY 10 planes is a pointless exercise. It just ain't worth it and I cannot imagine anybody is doing it on purpose. From that point of view, it really does not matter if a certain plane is ENY 5 or 8.
On the P51 vs La7 argument: I really don't see a big issue with that. While the difference in % seems rather big, the actual perks earned are still little. And that is what counts, you pay in perks, not in %.
As for the 51D being worthy of ENY 5 - You only consider A2A. The 51D is vastly superior to the La7 in A2G, much more than the La is superior in A2A. So, ALL things considered, the P51D is a better plane than the La7.
I have not seen La7 porking bases in any manner yet. But you see 51Ds doing that very often. So take its K/D ratio with a grain of salt, it's skewed by base porking deaths.