PrivacyWatchChat does NOT collect any personal data. Everything that WatchChat needs in order to work happens locally on your iPhone and your Watch. There is NO third-party server involved as your own iPhone is the entity that establishes the connection and therefore is doing all the heavy lifting. I can NOT see your chats, I have NO access to your data and there technically is NO way I could intercept your traffic. As this cannot be proven from my side you can check for yourself using a network monitor.
Syncing your quick replies with iCloud takes place within your personal iCloud storage that I do NOT have access to.
The app does NOT come with third-party frameworks that are employed to access your data. As the app does NOT contain any ads, your app usage will not contribute to such services.
Should you have any more questions about the app, do not hesitate to contact me at firstname.lastname@example.org, I am happy to help.