That's true. Like I said elsewhere, I really wish they hadn't made it a Kryptonite virus. I wish they had shown Jordan and Jonathan both reacting to the gas itself. We are comparing two different things really. And it leads to plausible deniability everywhere.

"Jonathan didn't react because he doesn't have powers." "The only reason Jordan was sick was due to Cold Breath." "Jordan would have been fine around the Kryptonite gas being released but had trouble breathing later due to Cold Breath."

I think it's just bad writing that they are treating Jordan as the Kryptonian brother and Jonathan as the human brother. Both are half and half. They should have some similarities and overlap as to how they do in certain situations. Their human side should make them different from Clark and their Kryptonian side should be different than Lois.