PF: Can a request for a part-time employment in Postdoctoral Fellowships be sent to REA in the Grant Agreement Preparation period?

In the MSCA Financial Guide (p. 12) it says that “Requests for part-time employment may only be accepted in agreement with the supervisor and beneficiary and with prior notification to the granting authority via the mobility declaration (see section 4 on the mobility declaration).” This would mean that requests for part-time employment should happen after the Grant Agreement has been signed.