I think it comes down to whether the main breaker and/or the conductors between the meter and the main breaker are factory installed and thus part of the listed assembly.
For example, if you have a meter/main combo and the conductors between the meter and the main breaker are busbars, or factory installed conductors or some such, you could well be violating the listing if you mess with them. You would generally need to have a separate meter and main panel, or else create that situation if you don't have it (say, but putting a new meter socket and j-box ahead of the existing meter/main).
I would try to give the AHJ something along the lines of:
"The existing conductors between the meter and the main breaker were field installed. These conductors will be tapped with [such and such hardware listed for the purpose.] The installation will comply with [such and such code articles that require space for splicing conductors inside enclosures, etc. etc.]. Etc. Etc."