>There's been plenty of evidence that nothing is recorded or sent back, hardly "absence of complete proof".

You may have a different understanding of the word "complete" than the standard definition.

Unless you are claiming the verifiers kept the watches being tested under constant survellance for several years, the proof you are alluding to may only prove that it is not routinely sending or recording data. It does not prove they can't turn it on whenever they feel like it, or when obeying a time-limited and geofenced mass surveillance order.