This change has not been mentioned in patch notes, but it has indeed taken place. Spell symmetry still continues inflicting 6000 oblivion damage to yourself (if mages guild passives are not taken) and while spell absoption passive in lady tree remains unchanged to the eye, it no longer procs the passive if (health) requirements are met.
The undocumented change or possibly bug (?) is really disappointing and ruins immersion, because oblivion damage coming from different sources are not treated equally, while being exact same damage type.

Noted. Thank you for letting us know.

I understand these procs being removed out of combat, but in combat, there was always cost assigned to all of these effects, especially regarding spell sym + spell absoption, since you had to use it really smart due to you needing to at least lose 30% hp and having 50% less shield & heal strenght afterwards for 4 seconds, potentially risking your own death, there was clear risk and cost involved in it and risk vs reward, less unreliable playstyles, should be rewarded more than standard 'lets stack stats' playstyles that always work and are safe bets.

Yeah, pretty disappointing I must say. Crossing my fingers that this change will be reconsidered. I understand the change (really, a bug fix) that was made concerning item sets, but I don't agree with self-inflicted damage no longer proccing this specific CP passive. Again and as others have said, it's a high risk, high reward playstyle that was unique in terms of dealing with sustain changes, and by no means was it broken or misused, in my opinion. By casting Spell Sym you are effectively taking Oblivion Damage, and should therefore trigger the passive if its stated requirements are met.