Gotta love flying this is not a rule change, MBF cover has always excluded work cover. What you've got to realise is if or when a work cover claim is denied or ceases MBF will pay out as usual. You just can't claim both at the same time.
With the MBF you are still entitled to other insurance income and to earn income in a non flying capacity. Other loss of license providers or insurers will offset against their cover but the MBF won't.