Surprising and possibly incorrect passing of InitVar to __post_init__ method of data classes

GitHub fields:

assignee = 'https://github.com/ericvsmith'
closed_at = None
created_at = <Date 2019-11-06.12:50:00.498>
labels = ['library', '3.9']
title = 'Surprising and possibly incorrect passing of InitVar to __post_init__ method of data classes'
updated_at = <Date 2019-11-06.13:36:38.021>
user = 'https://bugs.python.org/AaronEcay'

bugs.python.org fields:

activity = <Date 2019-11-06.13:36:38.021>
actor = 'eric.smith'
assignee = 'eric.smith'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-11-06.12:50:00.498>
creator = 'Aaron Ecay'
dependencies = []
files = []
hgrepos = []
issue_num = 38719
keywords = []
message_count = 4.0
messages = ['356125', '356128', '356129', '356130']
nosy_count = 3.0
nosy_names = ['eric.smith', 'xtreak', 'Aaron Ecay']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue38719'
versions = ['Python 3.9']