`testpaths` is ignored when specifying the config file with `-c`

$ pip list
Package    Version
---------- -----------------------
attrs      21.4.0
iniconfig  1.1.1
packaging  21.3
pip        21.1.3
pluggy     1.0.0
py         1.11.0
pyparsing  3.0.7
pytest     7.1.0.dev236+ge466a87bb
setuptools 56.0.0
tomli      2.0.1

Minimal example

# <dir>/pytest.ini
[pytest]
testpaths = tests1

# <dir>/tests1/test_1.py
def test_1():
    assert True

# <dir>/dir1/pytest.ini
[pytest]
testpaths = tests2

# <dir>/dir1/tests2/test_2.py
def test_2():
    assert False

Steps to reproduce

Run pytest commands from the <dir>

$  pytest --collect-only

platform darwin -- Python 3.9.6, pytest-7.1.0.dev236+ge466a87bb, pluggy-1.0.0
rootdir: /Users/pacahon/Downloads/tmp/pytest, configfile: pytest.ini, testpaths: tests1
collected 1 item

<Module tests1/test_1.py>
  <Function test_1>

$ pytest -c dir1/pytest.ini --collect-only

platform darwin -- Python 3.9.6, pytest-7.1.0.dev236+ge466a87bb, pluggy-1.0.0
rootdir: /Users/pacahon/Downloads/tmp/pytest/dir1, configfile: pytest.ini
collected 2 items

<Module tests2/test_2.py>
  <Function test_2>
<Module test_1.py>
  <Function test_1>

Expected behavior

1 collected item while executing the second command + testpaths info in the output headers (since dir1 is the rootdir). Something like this:

$ pytest -c dir1/pytest.ini --collect-only

platform darwin -- Python 3.9.6, pytest-7.1.0.dev236+ge466a87bb, pluggy-1.0.0
rootdir: /Users/pacahon/Downloads/tmp/pytest/dir1, configfile: pytest.ini, testpaths: tests2
collected 1 item

<Module tests2/test_2.py>
  <Function test_2>

P.S: I experience the same behaviour with 7.0.1 from pypi. 6.2.5 gives me an error ERROR: file or directory not found: tests2
P.P.S. Maybe related to https://github.com/pytest-dev/pytest/issues/9703

Reproduce the two pytest --collect-only commands using the shown pytest.ini files and -c dir1/pytest.ini. Start by tracing how testpaths, rootdir, and the explicitly selected config are handled during collection. Done means the second command collects only tests2/test_2.py and reports testpaths: tests2 in its header.