odgt shows what is available at driver level which is the average (possibly weighted) of all 3 values.
The chip has 3 temp probes. The chip feeds data to the board which is used by the bios to adjust fans, engage thermal throttling, etc. The driver pulls that data and reports it as a single value.
Software which gets all 3 values (and VRM values, and host of other great data from the bios that AMD feels is "unimportant") do it by querying the board at a low level not using the drivers.
Sadly AMD attitude has always been lets abstract stuff away via the drivers.