`formatStateUsing` not working when fields are loaded dynamically

Hi. I'm loading fields dynamically based on a select like this: https://filamentphp.com/docs/3.x/forms/advanced#dynamic-fields-based-on-a-select-option.

However I can't get

formatStateUsing

formatStateUsing

to work when switching select options. It only works for the fields of the option that's selected when the page loads. Anyone know why?