Tkinter and turtle graphics fill differs between Windows and *nix

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-02-14.19:22:08.730>
labels = ['3.7', '3.8', 'type-bug', 'expert-tkinter', 'docs']
title = 'Tkinter and turtle graphics fill differs between Windows and *nix'
updated_at = <Date 2018-06-16.20:14:29.099>
user = 'https://bugs.python.org/JohnSimmons'

bugs.python.org fields:

activity = <Date 2018-06-16.20:14:29.099>
actor = 'terry.reedy'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation', 'Tkinter']
creation = <Date 2017-02-14.19:22:08.730>
creator = 'John Simmons'
dependencies = []
files = []
hgrepos = []
issue_num = 29560
keywords = []
message_count = 4.0
messages = ['287794', '288050', '319754', '319783']
nosy_count = 5.0
nosy_names = ['terry.reedy', 'docs@python', 'serhiy.storchaka', 'willingc', 'John Simmons']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29560'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']