The dates mentioned in a retweet are actually from ASUS marketing person posted on Chinese Weibo. Those ‘big days’ refer to AMD B550 motherboards launch and availability. However, it is likely that Matisse Refresh could arrive close to those dates as well (if it is arriving at all).
3750X/3850X.....— HXL (@9550pro) May 22, 2020
Not APU https://t.co/GOz2JOHobW
A slide from the Gigabyte B550 press deck also mentions Matisse & Refresh so that's further evidence.
A slide from the B550 press kit.— Hassan Mujtaba (@hms1193) May 21, 2020
It seems to be before AMD announced Zen 3 support for 400-series.
Also, A520 - August 2020 pic.twitter.com/OkugokQzof