MS90 is not a failure to identify YOURSELF per se, it is a failure by the Registered Keeper to identify the driver (themself or someone else) at the time of an alleged driving offence, such as speeding or careless driving. If the driver is not identified a prosecution of the original driving offence cannot proceed therefore the second bite of the cherry is to prosecute the person who has a legal obligation to identify the driver (unless unable using reasonable diligence) i.e. the RK.
I don't know if DVLA is able to act on the information if you, as a third party, were to inform them that his address has changed but matey-boy has opened himself up to another maximum fine of £1000 for failing to do so himself.