well that makes sense, since in the second phrase the "both" can be easily exchanged by other word without harming too much the sentence's meaning

but I'll try to find the link again, I'm pretty sure they meant that "both is good" should be okay too, but you'll have to wait until I sleep and wake up again because it's late here and I'm on mobile

im probably just making a fuss after reading things wrong but I was really confused