I can only reiterate what a few others have said about what Anonba says being as close as it gets as having a living version of teh BA current policy, so to anyone finding it hard to believe based on other airlines, past policies, etc I can only say that sometimes, airline policies change in unexpected ways (there have been so many changes that have baffled me over the years, not all in a good way), not always forever, but Anonba is a source I absolutely would trust.

I would also point out that the implications are 1) a first voluntary change that includes ticket reissue followed by 2) a second voluntary change to a new date within the new validity period so just bear in mind that whilst this might look like a solution to a problem, it may also prove an expensive one as change fees will need to be paid twice and on most tickets, fare difference will go in one direction only - so for instance, if rebooking in September with very little time left implies a need to rebook into a significantly more expensive fare class whilst there would have been a cheaper fare available in May for now, on most tickets, there will normally be no refund from the higher September fare so it may well prove cheaper to just cancel the existing ticket, take whatever is left and then rebook the cheaper May ticket from scratch instead of paying it at the level of the last minute September ticket which may well be the implication of the two-step change.