> I'm saying that this tenet is misleading.

Doesn't that go without saying? There is no tenet that isn't misleading when presented to a general audience. Fair that if you come from a position where you understand the full context and nuance under which the tenet was built then you should be able to free yourself from being mislead, but, of course, this time is no exception.

> If several packages consume the same interface, then you it's not reasonable to define the interface at the consumer because you'd just have to copypaste it.

Where several packages find interface commonality, there is no doubt a set of "primary" functions that roll up shared functionality around that interface. The package of shared functions is understood to be the consumer under that scenario.

Where several packages stumbled upon the same interface without any shared functionality, copy/pasting is warranted. In this case, while the interfaces may look the same, they do not carry the same intent and that needs to be communicated. Another oft-misunderstood tenet, do not repeat yourself, does not imply avoid repetitive code.