In the absence of any ‘Case Law’ on this subject (that I know of) the position is that Insurance requires the person to ‘hold, have held, and is not disqualified from holding a licence (for that class of vehicle)’.
Notice here that the requirement is not for a FULL Licence. Merely a Licence for the class of vehicle. - Therefore any offences would only relate to the displaying of L plates and being accompanied by a qualified driver. - But you are a qualified driver, so you don’t need to display L plates. The Pass Certificate tells you that you are qualified. The only restriction imposed by that document is that you cannot accompany another L driver.
Going back to my distant learning of English Law, then once your application enters the Postal system, i.e. putting the envelope in the post box with the required fee, then the DVLA are contractually obliged to issue a FULL Licence. Offer, Acceptance and Consideration are the key works. They ‘Offer’ to issue the Licence for a set fee. You ‘Accept’ their ‘Offer’ by enclosing a cheque (Consideration) - A Legal Contract has been entered into.
I would have no qualms in employing a person producing a valid LGV provisional together with a Pass Certificate for that class of vehicle - provided it was less than 2 years old.