Getting number of parameters in FUNCNAME

Why does Snippet A

echo "params are ${FUNCNAME[@]}; param count is ${#FUNCNAME[@]}"

return

params are main; param count is 0

But Snippet B

_foo(){
    echo "params are ${FUNCNAME[@]}; param count is ${#FUNCNAME[@]}"
}

echo $(_foo)

return

params are _foo main; param count is 2

For Snippet A, shouldn't param count be 1, instead of 0?