They are trapped by EASA which means he needs IFR time to operate single crew commercially IFR.
Its been tried before to get hours counted IFR while teaching a PPL nav ex.
Its all rather dodgy to be honest. And pretty transparent what you are up to.
I know one person that managed it and another 2 that it didn't work for and one that got removed from flying after 4 months when the FOI audited the training files.
I can't give you any references though to say you can't.