It sounds like there are several inaccurate assumptions/misunderstandings in your initial question, and there also may be an XY problem involved as well. I will do my best to clear up any confusion and answer the intent of your question, please let me know if I misunderstand.
The maximum motor eRPM capability of an ESC is a fixed number determined by the ESC’s hardware and software capabilities. Beyond this point, the ESC cannot keep up with motor commutation, and cannot effectively drive a motor. It is a fixed limit.
There is no relation between number of motor pole pairs and max ESC eRPM that will affect no load or max motor RPM.
eRPM can be determined by the following equation:
(number of poles/2 * RPM) = eRPM
If you are using a motor with a maximum mechanical RPM of 9,000, and two pole pairs:
(2 * 9000) = 18,000 eRPM, which is far less than the 350,000 eRPM limit of the Basic ESC.
Your motor is well within the eRPM commutation limits of the BasicESC.