Hello !
I just linked a verified Uphold account to the browser on my computer that had about 11 BAT. Once I linked my Uphold account to the browser, I instantly received them on Uphold, and the Brave Rewards tab was showing the correct amount of BAT (as expected).
A few minutes later, I linked the browser on my old computer which had 179 BAT, and the previous 11 BAT were replaced with the amount I had on that old computer.
In the end, I lost 11 BATs, not a big deal, but I’m still worried that the same problem will occur when I connect my laptop to the Uphold account.