I was under the impression that it was the requirement of the council to follow legislated employment law not NALC recommendations or information sheets.
Holidays, pay, and requirements are required actions. What ids wrong with the clerk booking their annual required leave with their employers ( the council) and taking them before the prescribed cut off point during the year.
PC should have contingencies in standing orders, and the contract of employment, for cover during both known and unforeseen absences by the clerk