dataclass defaults behave inconsistently for init=True/init=False when default is a descriptor

GitHub fields:

assignee = 'https://github.com/ericvsmith'
closed_at = None
created_at = <Date 2019-11-30.23:53:26.972>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'dataclass defaults behave inconsistently for init=True/init=False when default is a descriptor'
updated_at = <Date 2020-10-18.23:48:06.146>
user = 'https://bugs.python.org/KevinShweh'

bugs.python.org fields:

activity = <Date 2020-10-18.23:48:06.146>
actor = 'iritkatriel'
assignee = 'eric.smith'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-11-30.23:53:26.972>
creator = 'Kevin Shweh'
dependencies = []
files = []
hgrepos = []
issue_num = 38947
keywords = []
message_count = 3.0
messages = ['357669', '378913', '378914']
nosy_count = 6.0
nosy_names = ['falsetru', 'eric.smith', 'Claudiu.Popa', 'levkivskyi', 'Kevin Shweh', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38947'
versions = ['Python 3.7', 'Python 3.8']