The lower tier armorings didn't used to be slot specific - but that was prior to 1.2 IIRC.
Wrong again. There is no gear of any kind where the armorings "didn't use to be slot specific", but now are.
If you are talking about some low level orange gear with blue and/or green mods and armorings (which I would not call "tier" gear) then the armorings from those were not and still are not slot specific, so you can move them to any piece of gear. No changes of any kind have ever been made to them.
As for the endgame tier gear that existed before 1.2 (tionese, columi and rakata) they used to not even be fully modifiable, but had only mod and enhancement slots, and the stats that would come from the armorings were built into the gear. So not only were you not able to move an armoring from them to another slot, but you could not even move it to another gear for the same slot as the purples back then did not even have removable armorings.
In 1.2 these items were changed to have removable armorings too, but these armorings were made slot specific.
These armorings have been slot specific for as long as they have been removable and before that they were not even removable at all.
Also any new gear added in 1.2 (black hole and campaign) had slot specific armorings right from the day they were added to the game.
No changes have been made to any of them since that
In 1.4 they changed many off-hands that were not previously modifiable to now be modifiable. These have an armoring that is not slot specific and can be put to any gear. Before 1.4 they were not modifiable and did not have removable armoring.