The requirement with a gearbox chip (which burns off) is to record it, and make sure you are not getting more than 2 per 50 flt hours.
With an engine chip, there is mandatory maintenence action before next flight. So, its logical you dont burn the engine chip on the ground, as you cant take off anyway.
So, an engine chip is more of an issue than a transmission chip - I guess the gearbox is more resilient to the occasional particle than the engine is.