Blurred battle reports were introduced to avoid espionage attacks, e.g., attacks with a low number of units, not to win the fight but to spy on the unit strength of the defender without using a spy unit, which is intended for this purpose.
So, if the game considers an attack to be too weak, the corresponding battle report will be blurred to prevent the attacker from seeing the unit strength of his opponent.
For such a report, the defender may see every unit involved; the attacker may only see his, and everything related to the defender will be blurred.