I personally think that the Scab Stalker is a ranged shooter, and after some testing, it does approach you when shooting, however, this is not the case in all cases.
When this enemy finds you, there are two possible situations.
1 It is far away from you, your ranged attack alarms it, or it is in the wave of an enemy attack, and it will shoot at you with a ranged attack as much as possible, rather than actively approaching.
It moves around, but most of the time keeps its distance.
This is because your ranged attack somewhat prevents it from approaching, and every time it tries to find cover, it doesn’t actively approach you.
Unless you abandon the ranged attack, it will actively approach you.
And it’s have the strongest ranged attack among common enemies, firing three shots bursts and damaging much more than riflemen using lasers or cultists with auto guns.
2 When it actively detects you at medium distance, it usually moves while shooting, and more than half of the time it will actively approach you.
But due to its higher damage, when it approaches melee distance, it has already dealt far more damage than other shooters in the same amount of time.
Another scenario is that it will constantly move around and shoot, but always stay at medium distance instead of entering melee attacks.
So, taken together, it is a ranged shooter overall, and the potential for ranged damage it deals is far greater than its melee threat.
I hope that developers will reconsider the positioning of this enemy, adjust its AI, or modify the veteran skills Counterfire to avoid misleading the player.