The difference is the legal burden.
If a Waymo vehicle causes an accident, then Waymo the company is responsible and accountable for the legal costs of that accident.
This legal burden is why they have lots of cameras, sensors, LiDAR, geofencing, mapping and redundancies built in to limit their exposure to risk.
Supervised FSD puts the legal burden on the driver/owner of the Tesla. Tesla the company isn't legally responsible for any accidents or mishaps on the road involving Tesla vehicles. Tesla vehicles don't have LiDAR, sensors and redundancies built in for safety to limit their legal burden. Supervised FSD Critical Interventions are still way too high for Tesla to assume this risk.
I think I would be way more confident in saying that Tesla has solved autonomy once they're confident in their own product enough to assume the legal burden. This risk would be absolutely massive considering the 2M+ Tesla vehicles out on the roads.