[mpalmer]

Tenet has a dictionary definition; as far as I can tell there's nothing to suggest that it's specific to some industry-speak concept.

If one is being super pedantic, tenets and principles aren't the same thing, but they're very close in meaning to each other.

The linked page contains examples of both tenets and principles, and uses the terms interchangeably in the title/intro.

Tenets are positions/beliefs/qualitative statements presented without proof. "The web matters", "No one cares" are examples from the OP.

Principles are related, but more like guidelines or instructions. "Optimise for vibes" is an example.