This was a fix for a special nullsec tactic, using swarms of nullified ECM ceptors. Long before nulli change. Now more ships can nulli, but suffer from this for them new drawback.
As always, if somethings becomes too common and easy, CCP will nerf it. So always pray your favorite ship or play style doesn’t have a top place on KB or makes nullbears whining.
I have no opinion on this one, not playing in null. But in general it’s a good nerf for haulers, the nulli module was a too big buff imo.
The high slot is the least restrictive, because ships “requiring” the module have spare ones. Not so much other slots. Remember you need a fitting upgrade on ceptors, or much reduced tank on top.
Well, I like my probe launcher, covert ops cloak, and salvager, now I have to drop the salvager on a 3 high ship for the nullification module, alternatively, 4 high slots will do then.
The nullification subsystem of T3Cs still exists and gives bonuses to the new high slot nullification module (same as interceptor bonuses, lower penalties, shorter cooldown, longer duration I think). No extra high slot though and any T3C can equip the nullification module now to become nullified regardless of subsystems so the nullification subsystem is pretty useless these days.