That's interesting. "mums good for cats" and a "mums bad for cats" gives the expected response, it's just "okay" being parsed funny. I've reported it to someone at Google so it'll get fixed... eventually.
It's also very non-deterministic. Not a 100% failure rate, seems to go up&down with time, and varies depending on plant/animal combination
Replacing “okay” with “safe” also fails
https://imgur.com/a/PgCzK1H
Kind of unbelievable 4 years into this hype cycle we still have basic issues like answering the inverse of users question