useFieldArray rules validate prop behaviour

[martynasgz]

I wanted to use the validate rules prop on the useFieldArray but realized that it behaves in a different way than I expected. It seems to validate only when the field array is appended/removed/replaced/... to, or the form is submitted. I'd expect it to validate according to the validation strategy specified in the mode prop of useForm, when the inputs of the field array themselves are interacted with. Is this the expected behaviour? Is there a way of achieving what I want? Here's the sandbox that I've modified from #8102 to display the issue: https://codesandbox.io/s/react-hook-form-usefieldarray-rules-forked-pj44rr?file=/src/index.js