When we first looked at the PTR we found instances of 'Identify Legendary'.
The idea seemed to be that whenever you loot a legendary, it doesn't automatically roll into whatever legendary it becomes – you need to 'identify' it giving you the time to choose your loot spec and then open it up and get your legendary.
This solution would have helped many people trying to transition or develop different specs and prevent the whole fiasco of accidentally changing your loot spec to something else.
As of the latest Q&A and clarifications, it has been removed: https://redd.it/5vujvi and https://us.battle.net/forums/en/wow/topic/20753190241#post-9
3) The PTR has had "Unidentified <Class> Legendary" items in its database for a while, and it's been speculated that these were a 'failsafe' for people accidentally getting a legendary in the 'wrong spec' and blowing their accrued Bad Luck Protection — are these unidentified items still going live
These were part of an experimental concept that we've since decided not to go ahead with, at least for now.
I'd settle for a different 'legendary loot spec', but this was a nice elegant solution for this conundrum. It allows people to farm legendaries for their Off Specs while they were weak, prevents accidental loot spec fiascos, and creates a decision matrix where you can decide which spec you want the legendary for.
Win-win. Why remove it?