This traces back to https://github.com/facebook/react/pull/6449 and then
another before that.
I think that back then we favored the property over the attribute, and
setting the property wouldn't be enough. However, the default path for
these are now using attributes if we don't special case it. So we don't
need it.
The only difference is that we currently have a divergence for
symbol/function behavior between controlled values that use the
getToStringValue helpers which treat them as empty string, where as
everywhere else they're treated as null/missing.
Since this comes with a warning and is a weird error case, it's probably
fine to change.
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