I would call it reusing an existing test-suite. However, that’s semantic nit picking.
I agree with you that finding a good format for Gherkin is hard. I started converting a HTTP Signature test from bovine to a feature:
https://codeberg.org/helge/fediverse-features/src/branch/main/fedi/http_signatures.feature
and the result is: I don’t like the result yet. This kinda is what I want when implementing. It provides the details to check when debugging, but it is not what a Feature should test. That should be more on the level of at least http signatures.
I however think that this is a step forward to a reusable test compared to the code in test_http_signatures.py from bovine. Even without knowledge of Gherkin / python, one should be able to write one’s own test from it.
Like many things, I think writing features for these things still needs time to mature as an idea in my mind.