This is a Wind 10 NVidia mining rig:
Both mining programs can be run at the same time. There's a slight profit loss but the cards haven't been optimized or tested yet to see if speeds can be increased.
https://www.pyramidreviews.com/bitcoin-mining/dual-mining-ethereum-and-zcash-or-other-equihash-coin/
Sorry to say that, but it's total bullshit. It's not working like that at all.
Check your measurement once again.
What part is total BS? The hash rates, or the fact that it's working at all?
On Wednesday I'll be next to the miner and I can re-check/re-measure