Perhaps Cristinel didnt express himself fine. But i do confirm at least the Title of the topic, the Profession Unique enhacementes, enchants, abilities,etc are staking. If you drop a profession and learn another the benefits applied to any item remain.
Pratical cases on my server under Mangos 10064 - UBD 391 - SD2 1713, the player has learned JC and BS, then he dropped BS to enchnat the additional sockets from BS did not become innactive, they remained on all items on which they were used.
Another case for a guy dropping engineering that has dropped it and remained with the Engineers only Mounts.
Also have seen JC that have kept JC unique gems on the item, dropped profession, and the item remained with the JC only gems active.
The same for Enchanters and Ring enchants.
I dont know while the same is happening with Tailoring, but as it is being seen in all other professions probably the bug applies as well.
How It Should be: Im not sure if the benefit effect should drop from the item toolip, but for sure once the profession is dropped it should become innactive with no bonus being granted.