Is this standard practice now?

[Ben Diesel]

I bolt the baffle into the (road legal) can on each of my two bikes before they go off for their MOT.

I've had a similar comment on each of the last 6 tests (three different test stations) - "It's passed, mate. But the can's a bit loud. We've given you an advisory for that.'

I'm a believer in the 'cover their arses' theory above.