In this primer there are no trees at all, only bushes (there was specifical question on the forum). Screenshots show that only tanks see each other because they see turret tops above the bushes, while less tall SPG and AT guns can't see anything. In current visibility system view is traced from top of the unit, sector visibility with modeling of pros (increased view range) and cons (greatly reduced field of view) of historical optical instruments like periscopes and optical sights will be in addon.
In addition, in described case (when unit knows there is enemy unit over there but can see only small part of the target) calculated accuracy error is multiplied by 3 times.
Un pequeño apunte

eL su-76 no puede ver al panzer III

El cañon ruso antitanque tampoco

En cambio el t34 si puede distinguirlo através de los matorrales(no son árboles) debido a su perfil más elevado.

El pak alemán es incapaz de distinguir nada

El stug tampoco debido a su bajo perfil

Pero el panzer III si puede distinguir al t34 debido otra vez a su más elevado perfil
Hay un poco más de información en la web de 1C
Saludos