Why doesn't Imperial Super Commando have the Imperial Trooper tag?

Because they are a Mandalorian house that aligned with the Empire, not Empire citizens trained as a trooper. TIE Fighter Pilot on the other hand most certainly should have that tag.

Tie pilot is pilot, not trooper.

Imperial super commando has Imperial in name title, and is a ground force unit.
(EDIT: also canon has been proven not to apply in this game. But I agree, the mandalorian house merits its own Mando tag, but I feel in-addition-to, rather than instead-of. Sabine needs that tag too. I’ve heard mixed reviews as to whether Boba should get that tag or not.)

Also, I feel like the new probe droid should actually have the trooper tag. Droid, but still ground force and fights alongside snowtroopers in Territory battle Hoth, so... (even the update letter recommends using him in trooper synergy squads)

He really should have a bounce back synergy passive ability with Gar Saxon, like Wedge and Biggs. They should lower his counter attack chance to 50 percent, but should share that passive with Gar if he's in the group. That way, both have 100 percent counter chance when paired together, helping to justify their low(ish) damage.,

"Sev112;c-1361512" wrote:
He really should have a bounce back synergy passive ability with Gar Saxon, like Wedge and Biggs. They should lower his counter attack chance to 50 percent, but should share that passive with Gar if he's in the group. That way, both have 100 percent counter chance when paired together, helping to justify their low(ish) damage.,

+1