The difference with emailing money on PayPal is that the recipient is notified. Brave was collecting currency on behalf of people without even notifying them.

Just because someone can collect the money/currency at a later date doesn't make it fine. If I collected money on behalf of charities yet only gave the money to the charity if they explicitly asked me for it, I doubt that would go down well with donors.

I could even use the situation to my advantage by gaining interest on the donations in the time between it is donated and I pass it on. I suspect Brave was benefiting in a similar way - all the donated money would not be traded while Brave were holding onto it, creating a scarcity which would benefit BAT's prices.