What is the meaning of non-string constraints?

[nicuveo]

It is currently valid (as in: does not throw an error, does not result in bottom) to do the following:

[int]: {r: 0}
"3": {r: 1}

That's because field labels will always be matched as strings when trying to evaluate constraints. Consequently, non-string constraints such as [0], [<4], [false], or even ['3'] (because fields are strings not bytes) will never match a field's name.

What's the rationale for silently allowing them?