I am pleased to see that there has finally been a resolution. I don't know what has driven this policy change but it's nice to see a result for most of us. It's been a long haul!
I think it's quite reasonable to expect to be able to change linked accounts from time to time. As technology matures and lets face it, data breaches do happen, people do have legitimate reasons to use different accounts on the same service.
As I said in the third post in this thread, there is no reason why the six monthly cooldown restriction couldn't apply to changing the third party account that is linked. i.e. One Xbox account every six months per EA account.
If this is an official EA policy change then it would be great if EA updated the information on the account unlinking page - https://help.ea.com/en/help/account/unlink-gaming-accounts-from-ea-account/ - which as of today still references the one account per lifetime policy. I was told by EA support on twitter to monitor this page as it would reflect any changes to the account linking policy.
CMs - I don't know if you guys had any influence in this change but myself and others did ask for updates several times between March and now but we didn't get much in the way of engagement. My frustration, and I suspect many other user's stemmed from the fact that we didn't feel we were being listened to. I would have been nice to have heard of this resolution from someone at EA rather than a forum user taking the time to let us know of his success. Maybe someone should do a blog post or something so that when the next person comes along searching they can find the correct information rather than wading through the first 27 pages of this thread.
Hat tip to @AssassinXDAhmed for letting us know - it's great that you took the time to post about your experience. You post is as close as we have to a solution so I will mark it as such.
Hopefully this change is solidified and communicated more clearly going forward.