Why didn’t they just use https://en.m.wikipedia.org/wiki/Certificate_of_Deposit_Accou...? I haven’t used it I just read about it in a Taleb book but it seems like it would be much easier than creating all the accounts yourself and you can interact with just one bank account instead.
I'll be honest, there's a chance that this is exactly what they did but that they didn't understand it or describe it properly. My main point was that there are ways to get protection beyond the FDIC limit, and your link shows a pretty reasonable way to do that.