Hi @Eiki, the default for V7.0.0 will be the Sangaboard V0.5. This then has a single power supply which is fed to the Pi through the Sangaboard. The electronics part of the documentation for V7 is incomplete and still being finalised to get from Beta to an actual release.
Without a Sangaboard V0.5, using either the Arduino Nano electronics work around or Sangaboard V0.3 or V0.2, it is strongly recommended to have a separate power supply. It is not so much about the typical motor current draw, but more about the consequences of failure modes. The motor current is not huge, but also not trivial. It also seems to be very variable across different batches - there are a few posts and treads about motors getting hot, for example Keyboard shortcuts and motor temperature - #26 by WilliamW.
The typical current that I measured of around 0.6A is within the capabilities of being driven from the Pi, but if there is a problem then this can go up, in the extreme case an accidental short circuit will give a very large current. Putting that current through the traces on the Pi circuit board is likely to damage the Pi which is an expensive part.
With the Pi 3B+ and earlier, an additional issue is that the power is delivered through a Micro-USB connector. These are not designed to deliver even the normal 2A that the Pi may need. Micro-USB connectors all seem to have a high contact resistance and cause regular low-voltage warnings on the Pi desktop. Adding more current draw by connecting motors just makes that issue worse.
So a single 2A or 3A standard Pi power supply has enough capacity, but you want to split the motor power off before the Pi. Then if something goes wrong you are most likely to damage only the motor and drivers rather than the Pi main board as well.
The Sangaboard V0.5 does all of this for you, and with a USB-C connector which is designed for the higher currents. Voltage warnings seem to go away on a Pi 3B+ when powered through the Sangaboard V0.5 because of the better power connector.