I disagree. Tesla is extraordinarily tight with a buck. They put in the absolute minimum that they thought would work. When they thought that they could do without radar, it was gone. When they thought they could do without ultrasonic sensors, those were gone. "The best part is no part." If radar is making a comeback, then the unit they've chosen must have significant bang for the buck. It may simply be a patch to address something that they just can't get vision to do, as opposed to trying to merge a more capable radar unit into their system. For example, it may only be for Automatic Emergency Braking and not for the FSDb system. Perhaps AEB is the root of all or most of the phantom braking issues and this is the only way they've come up with to solve that problem.
Remember too that Tesla has to install the sensor suite in almost 2 million cars this year, the vast majority of which are priced between $40,000 and $51,000.