I totally agree. We can spend hours talking about spotting problem or similar, but the truth is that we DO NOT KNOW how the Combat Mission engine models spotting and situational awareness.
It could be a bug or working as designed by the programmers (maybe a nearby friendly unit warned the TC or in CM tanks have a small chance to spot the enemy 360° even if buttoned, who knows?).
As a player I would like to have more detailed information from the game: spotting (which unit is spotting the enemy ones), mm of armour penetrated, etc. If this goes agains FOW, give us a "verbose" mode or a log file...
The more information, the better, IMVHO.
Bye.