This appears to have changed since I posted this and now it will query fold when types are changed in either manner.

I recently found this trick to improve folded queries when changing data types. It allows you to do type changes of columns without breaking the query folding. You can see if a step has been folded by right clicking on the step, if “View Native Query” is an option then the step has been folded. (Note that the opposite is not necessarily true, some sources do support some query folding yet do not allow you to see/edit the native queries.)