Looking at this example, phpstan correctly knows that bcadd will return a numeric-string (if given one).
But it does not do this for bcround.

https://phpstan.org/r/7155fd9d-b410-4ad5-883a-cd4c6af18ffc

I'd like to understand in which cases bcround can return non-numeric strings. According to php.net it "Returns a numeric string representing num rounded to the given precision.".