The realistic mode can optionally also hold your hands through many aspects of operating the aircraft, at a significant cost in performance, so more serious players will play with "simulator controls" (and will map more advanced things such as changing fuel mixture/prop angle/radiator activation, etc..., like you'd do on a proper simulator).
The developers in theory and sometimes in practice will correct inaccuracies in performance or capabilities if you can point them out from non-classified sources. Unlocking modern vehicles takes 100-600$ or hundreds (sometimes thousands) of hours, and sometimes due to inaccuracies they end up being or becoming non-viable, so some people are irrationally motivated to change that.
Whereas in a more crunchy simulation model, whether one plane beats another or something is going to be tied up in a lot more nuance.
Meanwhile the technical specs of the tank.... Those are absolutely critical because the damage simulation is entirely dependent upon them, because this isn't world of tanks where tanks have hitpoints. When you shoot a projectile, the projectile interacts with the armor, creates spalling (or explodes inside) that then has to kill all the personnel inside the vehicle for it to count as a vehicle kill. Shots that don't kill can disable parts of the tank, activate the ammo rack, destroy the tracks, etc.
A service manual isn't going to tell you how thick a specific section of the armor is, or what composition the armor has or what angle the armor is. Yes this still retains a sort of arcade simulation feel, because a realistic simulation such as this [0] is computationally too expensive to happen in a multiplayer game.
But I have doubts War Thunder is modeled accurately enough for a real service manual to actually make any difference for any of the players. War Thunder, from appearances, looks very arcadey and designed to be fun for most players. Sims usually involve 20 minute startup sequences, weight balance shifting, etc... I just don't understand this with War Thunder.