Two different taxonomies references are mixed

Reproduction steps:
1. Create 2 different taxonomies.
2. Add the same category inside each of the taxonomies.(The key should be the same)
3. Reference the first taxonomy in one document.
4. Try to delete inside the 2nd taxonomy the created key.

Expected result:
As there is no reference at all for the 2nd taxonomy I should be able to delete the category.

Actual result:
I'm not able to delete.
Error:
cannot be deleted because it is being referred to by the following documents