I don't think this is valid.  We will not have sting coordinates with bound values in any normal scenario

in this code new_bounds is only used as a container during the analysis of the collapse.

We are collapsing string coordinates from a categorisation, which will almost always only have points and maintaining a list of those points as a single composite point in the result.

I think this pull request should be merged and questions about how to interpret string bounds left to another day/activity