The simplified pictograms imply that in L4, one has to pay some attention and may have to take over. As
@diplomat33 pointed out, Robotaxis are L4 - so the extra Robotaxi column is actually complicating your chart. The customer (Robotaxi passenger) is never expected to drive the vehicle, but the same it can be said of a true L4 personal car.
The reason it's "only" L4 is that there are some situations in which it may not be able to complete the trip. This can be due to a number of factors, including map geofencing, weather conditions, traffic conditions, unusual local events or hardware failure.
(Noting that L5 basically means that none of the above can defeat the vehicle, unless the situation would have defeated a human operator also. Almost by definition, this requires artificial general intelligence and still may be unattainable unless the car can do things like send out a robot to clear away debris, change its own tire, open a cattle gate or negotiate with animals and humans in the path. So L5 is widely considered to be an unrealistic or aspirational level.)
(Also noting, for useful L3, napping or extended eyes-off is not out of the question. L3 can be like a chauffeur on the highway for example, but maybe not in town. An L3 vehicle will still have human operable controls.)
True, it's very common that people view L4 as "I
can take over but I shouldn't need to very often". Because most people discussing it have a driver's license and a personal car, so that's the way they're thinking about it. But in fact, a major use case for L4 is for people who cannot drive for one reason or another. (I'm very conscious of this because I expect this to be my case upcoming.) In any event, the real useful L4 will indeed be nap-time or back-seat passenger compatible. In the case of an L4 commercial Robotaxi, the fleet operator probably doesn't want any passenger intervention in any circumstances. So the L4 vehicle does not have to have human operable controls. Again though, the same can be true of a personal L4 vehicle; there's no fundamental distinction.
It's important to stress that the ODD limitations of L4/rlRobotaxi are not necessarily due to sudden unforeseen events, nor to solimple geofence restrictions. In many if not most such cases, the L4 inability to drive would be identified or predicted problems, before the drive even starts. These would come from known upcoming weather, road construction or closures, vehicle charge/fuel state and so on.
So as I've argued before, in those cases the car will decline the trip request, or at least warn the requestor that there is a realistic chance of a delay or an inability to complete the trip (usually solved by turning back or going somewhere else, but in the worst cases perhaps getting stranded and requiring outside assistance). For a personal L4 car, I believe that the threshold of acceptable trip-completion risk would and should be up to the passenger or guardian. For a fleet Robotaxi, the commercial entity won't be eager to take the responsibility ahd onsequences of a failed ride, so the acceptable trip-completion risk threshold would be lower.
Back to your chart: I'm not against the idea of simplified diagrams, but for this one I'm not sure I can suggest an alternate set of pictograms that impart the correct information. As you've already found in your second edit, it probably needs more of simplified text and less of somewhat ambiguous pictograms or symbols.
I'm also not saying I love the whole SAE levels paradigm, but it's what we have. Alternatives are proposed from time to time, but none I've seen are so unambiguous that they would end the endless discussions!