There is nothing in law, either national or European, to prevent a person being sent solo by an instructor as part of a course of training for renewal of an expired type or class rating.
ANO Article 60(2):
A person may act as a pilot of an EASA aircraft without holding an appropriate licence granted, converted or rendered valid under the EASA Aircrew Regulation when undergoing flying training, including solo flying training authorised and supervised by a flight instructor, in accordance with the EASA Aircrew Regulation as amended from time to time.
AMC1 FCL.740(b)(1)
Once the ATO has determined the needs of the applicant, it should develop an individual training programme that should be based on the initial training for the issue of the rating and focus on the aspects where the applicant has shown the greatest needs.
The ATO is perfectly at liberty to develop a course that includes solo flight if it considers that appropriate. What is not permitted is for an instructor to act outwits the course developed by the ATO and send a student solo when none is called for.