The lack of explanation is typical of EK middle management incompetence, much like the amendment to the additional fuel policy last year that was only explained about a week after introduction. What is really amusing is the incredulous comments from ATC when requesting the flights present Mach number. On my Europe flight today we had no less than four ATC requests to slow down due to preceding traffic and two requests to change levels due slower traffic ahead. All a bit of laugh really. I won't complain to much because I don't particularly want to spend any more time in the seat than absolutely necessary but a short explanation to the crews as to the intent of the policy might go some way towarpds making the crew feel part of this "Awesome Team" as I hear us described so frequently in the company rag.
Something big has precipitated this and I doubt that we minions will ever know the true reason but I don't see it lasting long in a practical sense, so enjoy it while you can.