Yes, my understanding is that during a flight test you are being assessed in accordance with Appendix I of the CAO and therefore shouldn't descend unless you're 'established'.
"Flight within the tolerances specified is necessary for the applicant to be
judged proficient in the required flying manoeuvres"
-CAO 40.2.1 Appendix I para. 3.1
Outside of your flight test/renewal, I can't see any reason why you need to refer to that appendix and could therefore follow the AIP instruction and descend once on a heading to intercept the outbound track.
Edited to add: The situation could potentially arise after a parallel entry if you elected to track back to the aid without intercepting the inbound track of the holding pattern. You may end up commencing the approach from the limit of the 30 deg.