I think this consideration cuts both ways–we can argue both sides of what is “historical” and what isn’t.
I think a more compelling reason for the rule is that it leaves a fantasy scenario open to the Axis, and there are many of those–a balance that demonstrates that the opening setup (as revised) is about as goldilocks as this particular game/map can get between what is Fantasy and what is Historical Reality (the Axis get slapped down).
Having attempted my own setups and game design, I fully appreciate the work and thought that went into the placement of literally every single unit and each rule, in each iteration. It still cannot strike an absolute “balance”, but that is nearly impossible in games where the opponents start with different units/territories/advanages (unlike chess where the only difference between the two sides is who goes first, that is a “model” game)
I think your point would be better made if the Japanese fleet was parked in the SZ to the left of SZ 26…not in it. Not scale wise but diplomacy/surprise wise. Appreciate the discussion.