I have had a couple of these emails and texts this afternoon too, and like you I couldn't quite square it with the increase in flights,
referenced here, just a few weeks later. I don't know if it's an equipment issue as the new NEO aircraft roll into the network.
I've had more changes on easyJet than on BA last summer, partly due to their use of Titan aircraft. But nothing really compares to how the USA airlines shake their schedules up. One of the perils of booking long in advance, unfortunately.