I have been using Brave for a bit now and I have serious doubts about how legitimate this operation is. Brave tokens disappear for no reason even outside of the supposed time when contributions are to be paid out. There is no audit trail to tell you why that is and the BAT disappearance is not shown as been related to anything, certainly not contributions.
What is more, the activity is not set up to benefit the user but those websites it contributes which seems to be all the ones that are VERY closely related to Brave itself. So in other words, this is basically a scam to entice people to go on to the websites of the developers and creators so they can funnel advertising money towards them while creating a false interest and surge in demand in BAT, which they end up owning anyway through this contribution system.
The fact that my BAT just disappears highlights that this is a dodgy scam that I have a feeling people should avoid.