2 week grace period for TPs

One of the BA Q&A articles on this site is about whether it’s possible to extend a BA tier point collection year. Quoting that article:

“On request, British Airways will back-credit flights in the first two weeks of a new membership year to the previous year, potentially allowing you to cross the threshold into Bronze, Silver or Gold… To do so you need to call British Airways directly… This is an official British Airways policy so you can call with confidence… If you do this, of course, the points will not count towards your new membership year. No double counting is allowed.”

I haven’t been able to find anything online to describe exactly how this works, so although it may be official BA policy, it does leave a couple of questions unanswered:

1. Can this be done only to retain existing status, or can it be used to gain a higher status than previously held?
2. Can it be used to trigger thresholds other than status, e.g. for earning Gold Upgrade Vouchers?

I have just called and asked about the second of these, and was told it wasn’t possible. This seemed entirely plausible but I wondered whether anyone else had ever tried it (or tried to used the grace period in any other way) and had any experiences to share. Also, is there any confirmation of whether the benefit will to continue to apply after the change in TP collection years? I don’t see why it wouldn’t, but again it’s hard to be sure when there’s no published rule that anyone can refer to.