Is that not intended behaviour? Imagine how it would look like otherwise, you wouldn't be able to suppress squad becouse one man is behind tiny cover. Or better, you would wire one man behind green cover in base and then move around all the other members freely without suppression.
I thought the "green cover symbol" shows up beneath the troop emblem as soon as more than the half of the squad is behind green cover, for example 3 out of 4 or 4 out of 6 models?