But you aren't trying to run both at max capacity, even if you are correct about the flow rates, which we will have to agree to disagree with.
Regardless, even if both were tuned to 500 GPH per drain there is no need to run 1000 GPH through a sump on a 100 Gallon tank. And a Herbie drain is self reliant. That's the whole point of the design aside from being quiet is that the secondary drain at max siphon will cover any clogs in the main line.
Having two is no more reliant than one. It just means you are tuning two drains for no reason, wasting money on a gate valve that's not needed, trying to force 4 pipes into a sump where typically people only use two for a regular Herbie and spending more money on plumbing. Just seems like a complete and total waste to me. One Herbie drain will easily Handle all the flow that is needed and be virtually silent.