Steps to reproduce:
Set Orion as default browser. Quit the Orion app completely. Open the macOS Notification Center and click on a Weather Widget. This will open a new Orion window with two tabs open, one with the weather as expected and additional Start Page tab.
Should open a window with only one tab with the weather. This is how it works when Safari is the default browser.
Orion and macOS:
Orion 0.99.109.1-beta (WebKit 613.1.12)
macOS Version 12.1 (Build 21C52)