How would not having pax or bags loaded affect a “compressibility” speed/Mach limit on the gear.
I think the question was more a case of "tell us all the details of the supplement, rather than just the height limit" ?
The report stated there was “no effect on serviceability of the aircraft” with having the gear extended above the FL150 limit?
I think you may have misinterpreted the statement. More a case, I suggest, of the minor exceedance not causing any associated damage .... as one would expect to be the case. There are very few occasions in certification where the aircraft is left near a cliff in the event of minor limit exceedances.
So what’s the limit for?
As suggested before, one would really need to be familiar with the certification reports, which usually are held quite proprietary by the OEM. Alternatively, one can engage in an extensive ferreting exercise in the design standards to see what possibilities might present.