This is anecdotal, but my GMC Yukon Denali using radar cruise control is much smoother than my P100D was. No phantom braking. It speeds up and slows down appropriately. I had all kinds of phantom breaking issues in my P100D. I realize that is not addressing the root concern here, which is radar. That said, even with radar, my Tesla struggled. Without radar, I imagine it will be even worse.
I see this as an attempt to widen profit margins. Sure, it gives Tesla an opportunity to continue to develop all the software and hardware behind FSD, but why else would you remove radar, when it clearly is beneficial in certain circumstances?