PyObject_Call not behaving as documented

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-12-13.00:21:25.725>
labels = ['expert-C-API', 'type-bug', '3.9']
title = 'PyObject_Call not behaving as documented'
updated_at = <Date 2020-12-16.14:42:35.640>
user = 'https://github.com/maxbachmann'

bugs.python.org fields:

activity = <Date 2020-12-16.14:42:35.640>
actor = 'josh.r'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['C API']
creation = <Date 2020-12-13.00:21:25.725>
creator = 'maxbachmann'
dependencies = []
files = []
hgrepos = []
issue_num = 42629
keywords = []
message_count = 2.0
messages = ['382927', '383173']
nosy_count = 2.0
nosy_names = ['josh.r', 'maxbachmann']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42629'
versions = ['Python 3.9']