What an imprudent title.. One difficult experience does not make a change of policy.
Perhaps it should be changed to avoid misleading readers?

OP, just to add that this is not to underestimate that this is a frustrating experience indeed, but be assured it certainly is an error (and sadly no surprise to those of us who know how rubbish BA it tends to be! ) Whenever you experience such issues, don't fear the worst as in a policy change and remember that you can always call BA and their service centre should be able to help you. It's obviously a lot less convenient than being able to do it directly online, but still better than not having your seat assigned at all!