[Safari 14][SameSite]Cookie is blocked when SameSite is set to Lax

Reproduce Steps:

1. Use window.open to open a new tab in Safari 14
2. In the original tab, using JS to create a FORM in the new opened tab and submit to redirect to a specified URL
3. The cookie info which's SameSite is set to Lax is lost in the new tab.

The reason should be, Safari 14 consider this scenario is carrying over cookie info from one tab to another tab and then block the cookies with SameSite set to Lax.

However, actually the FORM is created and submitted in the new tab, there is no CORS happens, Safari should not block the cookie.

Safari with old version and other browsers all will not block the cookie in this scenarios, so we consider this as an issue of Safari 14, please help verify. Thanks.