As you can see on the new URL, the guy specified :
! 2021/01/08: There has been a major change to the mirrors, check the repo for the new mirrors.
! Old mirrors will be deprecated in 3 months. The main download link “curben.gitlab.io/malware-filter/” is not affected.
The message is from early January and the last update of the current Brave mirror is 14th March. So it makes sense.
Therefore there IS a need to update the mirror for Brave, else we’re just gonna have a filter list that will become obsolete over time.