Karelian that simply is not true. In combat mission it depends on your realism settings.
With the c2 network below, this depends a lot on if you have kept platoons and up in contact properly.
Because squads don't carry radios but the CO of the platoon does... so the squad visually or by shouting passes on information to the squad command section who has a radio and passes it on to other platoons etc. This all takes time in game and if squads are out of contact may not happen at all. Often a whole game is fought with a unit not knowing what it is firing at other than that they are enemy.
From the manual:
"
Spotting and Contacts
Once your scouts are in position, you will start to see some enemy (grey-colored)
floating icons appear. The act of your units seeing enemy units is known as
spotting.
Spotting is a rather complicated affair in Combat Mission, but basically consists
of seeing confirmed enemy units, which are signified by a floating icon that
can be selected, and contacts, which appear as floating icons with question
marks. A confirmed enemy unit is straightforward: at least one of your units
can see it, and confirm its basic type, such as a soldier, an anti-tank gun, or
a vehicle. Your units will automatically fire upon these units as they see fit.
Contacts, on the other hand, are merely possible enemy units: your units think
there might be something there. Your units will not automatically fire at
contacts. The opacity of a contact will tell you how confident your troops are
that something is there: a very translucent contact is less certain than one
that is fully opaque. Contacts can be upgraded to confirmed units over time,
by moving closer to the contact, or if the enemy moves or fires at your units.
Units that move or fire are much easier to spot. Contacts can also be the last
known location of confirmed units.
Unlike the "Borg" spotting seen in most games, where once spotted a unit is
automatically seen by every enemy, units do not automatically share their
spotting with all friendly units: this is known as relative spotting. For
example, if one of your units spots an enemy anti-tank gun, a nearby unit
might not see the same anti-tank gun at all! The unit will have to spot the
anti-tank gun on its own, or have the information passed to it through the
C2 network. You can tell which of your units can spot an enemy unit by
clicking on the enemy unit icon. Your units that have currently spotted and
confirmed it will have highlighted icons.
You may have noticed that right at the start of the scenario some contacts were
visible: this is known as pre-battle intelligence, and tells you the location of
some enemy units at the beginning of the scenario. You, or your opponent,
may receive this bonus. Whether a side receives pre-battle intelligence and
how much will vary based on the scenario."
See how this guy is out of contact with his parent and sister units in the platoon (the red x) and can only see and shout to communicate. So he is now on his own for spotting.