I'd imagine that cancellation of ptz warranty (as defined upfront by them defining a warranteed cycle number) would make sense, but if the owner then wants to open-up and service their camera, and have it continue to function, that should be up to them. They own the product. And opening the product itself here (United States) is not enough to void any remaining warranty.
Of course country-specific consumer protections will further define what is acceptable. If Dahua had a 3-year warranty for country-specific markets, and they don't define exclusions in the warranty terms (contract), then they would still be required in many jurisdictions to service or replace the unit, even if it had "too many" ptz cycles. The question often comes down to the cost of litigation if the company refuses, and breaches the warranty contract. Here in the US, the cheapest recourse is small claims, even for them bricking the ptz after so many cycles. Beyond that, it's often the reason why class action lawsuits get filed, instead of individual lawsuits that would cost more than the product.
Buying through Andy, I believe we get a lower 1-year warranty, although he/they have been helpful well beyond this period of time. It would be nice to see a modified firmware.