Finally, some data that's not completely ambiguous!
Here's a plot of alerts in inhabited systems versus alerts in uninhabited systems, per week, per maelstrom, ignoring the first few weeks for each when they were doing that weird oscillating thing. (I've added a bit of fractional random fuzzing to the counts so you can get an idea of how many points are clustered together)
As you can see, six of our Maelstroms can be explained by a very simple model: they get 20 points a week to spend on Alerts, and inhabited Alerts cost 4 points each. So they can do 5 inhabited, 4 inhabited+4 uninhabited, 3 In + 8 Un, and so on. None of them have picked "we're feeling peaceful this week, 20 uninhabited" yet, but it seems to be an option at least theoretically available to them.
Thor and Leigong (highlighted with '+' rather than 'x' markers) do not follow this model - they generally (but not always) get fewer total Alerts than would be expected. Possibly their long range alerts are more expensive too, or maybe something else is going on? This needs more investigation.
EDIT: it may just be that Thor and Leigong have not yet exited / only recently exited their initial deployment phase - Leigong's last three weeks have been on the normal pattern, and maybe Thor just hasn't settled at all yet. All "initial deployments" have resulted in fewer Alerts than expected.
Why Leigong and Thor are taking so long to establish themselves I don't have any idea about - it's certainly not because we're excessively resisting them!