You seem to be implying that the cruise control will only use regenerative braking and not hydraulic braking when it wants to slow down. Forgive me if you've already explained why think this is the case in a prior post that maybe I missed. Or maybe I'm misunderstanding your current post. When I look at that schematic, it suggests to me that the computer is potentially able to use both kinds of braking, and surely the AEB system is capable of using both kinds of braking (it would be a pretty lame system if it couldn't do that), so I don't know why the cruise control wouldn't also be able to use both in the test you've suggested.At any speed, the motor slows the car first until the demand for deceleration exceeds its ability and the hydraulic brakes add deceleration. The motor is quite capable of moderate deceleration at any speed short of emergency or really brisk braking. Belief systems (not sure what you are trying to prove) are quite powerful, but here is a test you can easily do to demonstrate this. Set your cruise control say at 70 mph on an empty road. Now use the steering wheel controls to drop the set speed to say 40 mph. I think you would agree that that is pretty brisk slowing, probably brisker than you do on a daily basis (it is for me although I will do exactly that if I exit too hot). That is all motor. You can duplicate the same effect with just the brake lever. Where belief comes into play is that you are arguing that the hydraulic brakes are also activated in moderate deceleration scenarios (apparently you think a number on the speedometer matters). That is not how hybrids work or are designed, and would lead to less energy recovery and faster wear on brake components.
Any hydraulic valving and systems are irrelevant until hydraulic braking is activated after deceleration needs exceed that which the motor can provide alone. If you want to puzzle out braking engineering from diagrams, that's fine, but that has nothing to do with initial deceleration provided by the motor.
You can easily access thousands of articles that detail how hybrids work, again, kind of a silly debate here. They work by recovering energy from slowing, brakes work against that main goal.
On a slightly tangential note, I've observed that the cruise control accelerates and decelerates more aggressively than I usually do. I chock part of that up to "short sightedness" - it clearly doesn't see everything I see (like the guy in front of me in an adjacent lane getting ready to pull in front of me) and it doesn't anticipate as well, so if I'm letting it manage the speed in heavy traffic, there are times when it waits longer than I would to decelerate, and then it has to decelerate more quickly. Ditto for acceleration: I was driving this past weekend in EV mode with a nearly full battery, but with CC dialed in at 70 MPH. We hit a hill and I was annoyed that it started the ICE for a few seconds to get up the hill; pretty sure that if I'd been running the throttle, I might have slowed down a bit, but the ICE would not have started.