Yes it could, or it could be slower or there could be no catch up. A long haul A343 infront of a short haul B738 or A320 is a very quick catch up. In fact even a DH8D will catch it until the big bus finally finds the go faster button. My point is, even with nothing in the sky within 200 miles, we are not allowed to cancel the speed restriction unless for overriding safety reasons, what ever that might be. Allowing or even instructing aircraft to accelerate is, or rather now, was, a very useful tool, which is now not allowed to be used.
I too had heard it was possibly to do with avoiding action turns, but if that is the case, why is it not a blanket ruling for ALL traffic not just departures from some but not all airfields, and not for arrivals and overflights, and why only up to FL100?
Experience is the key to this matter, and it is being lost by this blanket ban. How many newly valid ATCOs know now that Swiss would never accelerate over 250, Tarom would do mach 9 given the choice, An Egyptair A340 will be flown like it's a hire car whilst Virgin A340s fly like a mobility scooter etc.