Happens just once when after install.
Pinning to task bar makes DEV tag go away, when pinning out, tag doesn't come.
But after that pinning again makes tag come again, and now never goes away when pinning or not.
(Running Windows 10 Pro for Workstations, 17763.379 with DEV channel of EDGE Insider)
@djraymond1 That is an interesting find. Thank you for bringing this to the attention of the Microsoft Edge Insider Build team.
April 09, 2019