python_use_unqualified_type_names does not work on function descriptions

[felix-hilden]

Describe the bug
When combining the new python_use_unqualified_type_names configuration with autodoc_typehints='description', the type names are not shortened even though links are created.

To Reproduce
Here's a minimal project using Sphinx 4.0.2 on Python 3.9:

# conf.py
import os
import sys
from pathlib import Path

# Insert source parent folder to path
_root = Path(os.path.realpath(__file__)).parent.parent
sys.path.insert(0, str(_root))

extensions = ['sphinx.ext.autodoc']
master_doc = 'index'
exclude_patterns = ['_build']

autodoc_typehints = 'description'
python_use_unqualified_type_names = True

# package.py
class A:
    pass

class B:
    def __init__(self, a: A):
        self.a = a

.. index.rst

Package
=======

.. autoclass:: package.A
.. autoclass:: package.B

This produces documentation looking like this:

Expected behavior
I'd expect the link to be shortened to A like it is when autodoc_typehints='signature'.