The rotary axis is controlled by a stepper motor. This is not a usual turning lathe. The rotary axis can be made as slow as necessary and the only relevant analysis is a quasi-static one.
Answering to parent comments: there are usually no encoders on these machines. The controller firmware just counts the motor steps. If a motor misses a step, everything will be off from then. For the cantilever design: it is already used by Prusa 3D printers which are well regarded (in the field of amateur 3D printing) so I do not think this is an issue for the targeted accuracy which is typically 10 to 50 micrometers.
The only issue I have with this design is that the accuracy decreases with the distance from the rotary axis, hence it is not uniform over the building volume.