Yea, waves (whether normal, raid engine, or whatever) that aren't launched directly at a human planet are just threat. CPAs are just threat.
Threat doesn't attack unless it thinks it has some kind of chance of victory. I understand that this may be frustrating at times, but ultimately it's just really stupid for the AI to throw units into defenses that are just going to maul it, and having the AI make lots of really stupid plays isn't really going to help the game be more fun.
So there's the waves as probing attacks, which (so long as you have an AI warp gate somewhere on your border) go directly into the teeth of your defenses. Nobody on either side expects those to win a game, they're just there to probe your defenses at different points with different unit combinations and maybe cause a ruckus if you've made a mistake or it lands in the middle of general chaos, etc.
And there's the exo strikeforces, which ARE intended to potentially win games, or at least knock out an irreplaceable or two. So they go in regardless, and hope that the rest of the galaxy can provide the necessary backup. They're also only launched in response to superweapons (FS, etc), so it's one of those "if we can't hurt the guy with the really big guns we're going to lose anyway" situations.
But the rest of the threat is very much supposed to just bide its time if your defenses are too strong for it. To do otherwise is for the AI to just throw away a strategic advantage. And if you're playing an FS game like the save you posted, then frankly it takes an enormous amount of forces to even pose a credible threat at all. As can be seen in the fact that the 20,000+ ships that (after I fixed the bug) balled up and tried to punch through Fiha failed to do so. And that was against your unattended defenses; I just watched.