All that tells you is that they are cautious in the famously litigious California yet confident enough to actually launch their service there. In the unlikely event something goes wrong, even if it is not their fault, they had a person onboard. It's the difference between that being just a minor incident or getting a class action lawsuit with millions/billions in damages. The law is by far the biggest obstacle to level 4 and 5 driving. So, launching in San Francisco is kind of a big step for them.
Once it has proven itself for a bit of time and they know how to set up their geo-fences and which streets to avoid, they can probably get rid of the person. That would be evident by that person never actually doing anything long before that.
The remote safety monitoring is a smart feature but it's not going to help much for the type of accidents people worry about most where something unexpected happens very rapidly. AIs are actually really good with dealing with those situations. Arguably better than humans for whom this is probably a leading cause of traffic fatalities. The way Waymo operates without hands on the wheel (i.e. level 3 & 4), basically means they have safety nailed already in those kind of situations.
There's no way a remote person would be quick enough to intervene. That person is there for other reasons. It's complex traffic situations that cause AIs to get stuck occasionally that require human intervention. Usually this is less of a safety concern and more of an annoyance.
The key metric of interventions per hundreds of thousands of miles of distance traveled is the key metric that both Tesla, Waymo, and other companies use for this. Both companies boast some pretty impressive statistics for that. Though of course it's hard to confirm those independently.
It's interesting the way Tesla and Waymo approach this problem in different ways. Waymo goes for level 4 but only in areas they've thoroughly vetted. It's taken them many years to start moving to new areas other than relatively safe and easy Phoenix. Tesla on the other hand offers their AI features just about anywhere they can but positions it as level 2 that is really aspiring to be a level 4 but with a requirement for hands on the wheel just in case (which means it's level 2). Level 2 is a legal tool to dodge a lot of legislation and bureaucracy. It basically means that if anything goes wrong, the driver is at fault. It will stay in place a long time for that reason. Liability, not safety, is the key concern here.
Arguably, Teslas would probably do pretty well in the areas that Waymo has vetted as well. But they are not in the ride sharing market and need to sell cars world wide and not just in specific geofences in Phoenix and San Francisco. But I wouldn't be surprised to see Tesla offer a similar ride sharing service in similarly geo-fenced areas at some point to get to level 4 & 5. I suspect that race is a lot closer than some people seem to think.