From the 5.036 patch notes (when brutal picks were added):
Previously it was possible for AI Homeworlds to get really brutal combinations like an AI Eye + 3 (or more) Core Raid Engine guard posts (which is pretty much the RNG saying "good game" on higher difficulties but you don't know until you scout it), or nothing really all that threatening at all. Randomization is core to AI War, but this particular bit of it could literally be the difference between a fairly easy endgame and a mathematically-impossible-to-win situation.
Now, for AI Homeworlds, it randomizes the three most brutal structures (Core Raid Engine, Core CPA, and AI Eye) separately from the rest of the structures:
- On Diff 9+ it always gets two picks from this new set. So you could get an Eye + a Core Raid, or two CPAs, or two Eyes (which is actually kind of nice to you since they don't really stack), or whatever. But not 3 Core Raids. And not none of the above.
- On Diff 8+ it randomly rolls (per homeworld) between one and two picks.
- On Diff 7+ it always gets one pick.
- Below Diff 7 it randomly rolls between zero and one picks.
From 5.046 patch notes:
When an AI gets 2 "brutal" picks for its homeworld (only happens on high difficulty), it now cannot pick 2 AI Eyes, since that's too nice.
From 6.006 patch notes:
Core Eyes, as a group, are now roughly as likely to be picked as each of the other brutal-pick AI HW structures. Each core eye is still equally likely to be picked, compared to other eyes.
So that's 6 brutal types. On 9+ you get two on each home world. That's 20 possible combinations, excluding double Eyes (6C2 with repetitions becomes 7C2 without, minus one for double Eyes). Of those, only 5 contain an Eye. So only 25% of homeworlds should have a Core Eye. There are two homeworlds, so the chance of getting a map with no Core Eyes is 56.25%. So with some quick math, we get Mean of 8.75 maps with at least one Core Eye in a sample of 20 and Standard Deviation of 2.22. So you are a touch over 5 Standard Deviations off from the expected result, or 1 in 3,488,555.
Although the sample size is small, that suggets that maybe something is off.