It's entirely plausible that the Hong Kong police have assembled a documented narrative of incidents of crime and abuse. The call for evidence into what might be a handful of cases isn't interesting.
What is unconvincing is that an app's potential to be used with crime is sufficient for people to understand Mr. Cook's bright-line, process, or thinking around the matter.
This app was likely being used in ways which critically supported the mitigation of risk to life, a fact which Mr. Cook described only as "benign"; the failure to discuss the balance against the app's relation to public health, and the failure to frame the nature of Hong Kong police and law, makes any attempted weighing suggested by Mr. Cook to be of low credibility as a lens into his process.
Presumably Google Maps, Search, and other apps also facilitates crime at a magnitude well beyond the app in question, but how does the weighing work?