Limitation of the `str(` function

In a separate post (, Dave Thompson points out that in Panorama 6, the str( function kept 15 significant figures by default whereas Panorama X keeps only 6.

This strikes me as an extraordinary and contra-intuitive situation. I would expect the string conversion of any number to replicate the value of the number up to the allowable number of significant figures. I doubt that I’m alone in that view.
Is it possible to modify the function so that it does what it did in Pan 6?