Yes it had. At first it was post-factum hauling of MA's.
Then you could prevent the station from shut down by supplying MA's in advance. After that UA's had no effect IIRC.
You really haven't been paying attention have you
If you'd been watching the galnet report on bombed stations you'd have seen the list increase in the last few months from 4-6 up to 30+ - it was out of control.
And why would that be? Well, FD had added bigger CRCR, and then added missions that dropped the availability of MAs from Darnielle's to a less-than-stunning ... one. Yup - one. Basically FDev unbalanced the attacker / attackee balance, and then decided to pull the whole mechanism because.
Not a fan of UA bombing, but even less a fan of this method of fixing it.