Your question is valid one, I think buffer wallets are best because the management of books is easier with buffer wallets then burner wallets, It act as a single middlemen, while there willl be numerous burner wallets and keeping the track of the funds is very hard. Collector module looks like a smart contract operational module and I don't think they have to get it from someone else they must have made it by themselves.
I also had the same question about $30 fixed amount, but I think someone has already asked this question but I guess not here in this ANN, well let's hear more from the team on this.
So you was right because the team has answered the same thing, they chose buffer for easy management of funds if the tx gets stuck and the collector is also their own development so that's a releif side because if the core systems of a projects are made by them then it is already safe but if they are using third party, that's not good for the long term working of the platform.
You should read their reply to me they have explained the reason of why the amount is fixed, just to ease it for you, it is about the dust in the wallet that sometimes left behind because of being so small that blockchain doesn't process it, you must have the idea what it is.