Steve,
Steve,
There are two batteries in the RAV4 Hybrid, both of which must be charged to start the car. One is a small 12V battery, which I think is located in the trunk (boot); this battery can be jumped via the terminals you describe. The issue I was referring to is discharge of the large "traction" battery, which is a crucial part of the hybrid system. This battery cannot be jump started on the road; if it discharges, the car needs to be towed to a Toyota dealer.
Now I'm at the limits of my knowledge about the RAV4, I don't know the circumstances under which the traction battery can become fully discharged. I believe it can happen if you inadvertently leave the hybrid system engaged for a long period of time, for example when the car is parked for a few weeks. But I'm not sure.
The point of my note is that due to the design of the "smart key" system it is easy to accidentally leave the system engaged. toyota is fixing this in the 2020 model, but it is definitely an issue with the 2019 and earlier vehicles.