I think it is written in this way because not all cards have CA. As I have noticed it in rules the big value cards do not have CA, so you can not play them although they might be the same attack type you are using this round.
it seems only combat cards of value "4" haven't the counter icon, but it's correct (4 is the max attack value, so it's impossible to start a counter with it).
so if you play at the combat round's start a "4" attack card, there are 3 possibilities_
1) your opponent uses an attack card with lower value than yours (from 1 to 3) and with the wrong counter icon (ex. you use a 4 melee attack, your opponent uses a 3 magic attack, that can counter only ranged att, not melee) so you win the round
2) your opponent uses an attack card with the same value (4), having a stand off. if both use a 4 attack card, none can counter (if is true that all combat cards 4 have not the counter icon as seems).note that if the stand off happens with lower attack values, it is possible to counter (rules, pag. 18)
3) your opponent uses an attack card with lower value than yours (from 1 to 3) with the right counter icon (ex. you use a 4 melee attack, your opponent uses a 1.2 or 3 ranged attack, perfect against melee). if he can (and decides to) counter, he has to play more ranged attack cards to overcome your 4 (he is able to do it? he win the round! no way to overcome your 4?if even with the counter his total attack value is smaller than your he loses, otherwise if he reach a total of 4 a stand off happens.
It should be right but I cannot be sure 100% until the game is in my hands. i can wait no more!!!