I get the same thing on Brave and the same thing happens. Since both Vanadium and Brave are based on Chromium and both have the same behavior, I'd say this has to be an upstream issue.
I also find it annoying, but I just tap the notification so it's dismissed. I know it doesn't do anything except dismiss the notification since the tabs won't be there when the app is launched next.
Until Google fixes the issue upstream you could just disable that notification channel, disable all vanadium notifications, or minimize the notification so it's less annoying.