No. After the HS XOSC is selected as the system clock calibration of the low power RC oscillator is initiated. The low power RCOSC calibration takes approximately 2 ms. Except for the first calibration after the HS XOSC was set as source for the system clock, a calibration will be aborted if one of the following actions is initiated by SW:
a) Switching the clock source for the system clock from HS XOSC to HS RCOSC
b) Entering PM{1 - 3}.
This means that if you try to enter PM1 once the HS XOSC is selected as system clock, PM1 will not be entered before the calibration is completed. You will not need a delay, but need to have in mind that there will be a delay before PM1 is entered.
BR
Siri