If you mean the spar yes, the wing will take punishment otherwise.
You assume aircraft skin is the main way an aircraft supports it’s structure, aircraft skin just provides the aerodynamics needed for lift, it doesn’t suffer “structural failure” just loss of lift, we assume each 20mm makes a hole of around the size of a human head then it simply need more than 5 shells.

You think 2 of these will split a plane in half?
Because I told “cannon =/= enormous cavern made upon detonation” and “aircraft structures are help up by the airframe and not by skin”
See how you need to destroy a vast number of
and losing lift at wingroot doesn’t mean it needs to snap off and nullify lift from the wing tips too.
It also means you let get away, drag is no joke, it slow down your plane to a crawl and is only made worse the lower you fly.
If you are shot somehow by such a beaten up plane that mean you went into a head-on while having an advantage OR you simply didn’t notice a slow moving plane crawl behind you and shoot you down.
If you really couldn’t stop him then that means the opponent used it’s armor as a last trumpcard OR he unironically planned it’s escape route well because the only way it can escape is that it runs to it’s team.
Transition 20mm damage to be more similar to a beefed up 15mm damage.
Will lead to make aircraft more distinct and model upsides normally nullified because 2 20mm shells aimed at enormous “weakspots” will nullify them.
And also calculate the amount of fragments based on filler compared to caliber
More filler = thinner walls and thus less fragmentation, however if you land it near or on top of an aileron, spar, rudder, elevator, fuel tank, etc. (And also it won’t black out stuff, orange red should be max so mg151/20 doesn’t become a broken mess)
Less filler = thicker case, more fragmentation, it won’t do as much individual damage to afforementioned modules but it can land really far away and still hit them. (Made so ShVAK doesn’t become ass but will put in it’s place)
Then AP will be more relevant because armor will stop explosive shells that land in your tail (they won’t cut it off as easily anymore) or even on your wing root if your plane has armor on the sides.
You posted your proof with 12.7mm but with 20mm that P-40 would have been split in 2 long ago.
I say yellow shells because they all deal the same damage.
hispano 404’s hei is the same as hei-t despite the first one having a 33% increase in explosive filler, literally no difference.
outside of mg151/20 which deals 1 extra tone of red, but only seen if you shoot a bomber.
1- I never said One shell is all you need, you need 2.
2- It’s Japanese, random chance to spoff because formulas are off by some number. Compare Russian 20mm hef to Japanese hef and see it for yourself, hell compare russian 12.7mm IAI with Japanese/Italian 12.7mm hef-t.
3- Only from the directly in the rear, otherwise you just cut the plane apart to pieces.
Which also made aircraft with more than 2x 20mm be merely more redundant in headons and usually suffer from higher BRs because of it.
Makes 20mm eat away at 23mm or 30mm in terms of damage because it doesn’t matter if damages 3 sections instead of one, I just need 1 to be destroyed.

Read below it and see how many other factors you are missing.
And planes that do are simply split in half
also a low AP performance means you need to be closer to your enemy in order to pen their armor or you know, shoot at the deflection shot and either cut both wings off or cut the tail.
Like it is currently, You need to play outside of Japanese TT
So are bombers durable in your definition? Also IL-10 is the only plane with a beffed up tail section and isn’t a bomber. That is the durability a B-17’s, Ki-49’s or Sunderland’s tail has in-case you don’t know.
Also only IL-10 has a tail like that, most Il-2s have normal super weak tails.
Because a BF-110’s tail is weaker, A mosquito’s tail same case but it sometime doesn’t detonate explosive shells, A beaufighter tail is weaker, a Sm.91’s twin boom is weaker and so on.
Wow 1 plane has a special exception where the tail that can survive more than 3 shells!? Revolutionary!!