I may be wrong but I don't think it has ever automatically re-loaded those from disk. It always preserves the state the panel was last in, including any edits made to the filters. (Could be quite bad if it didn't and you made a complex filter but didn't remember to save it, then need it again.)
What may have changed recently is that it now correctly says "* modified" on re-open when it didn't previously, but the content of the filter itself (including any edits made to it) has always been preserved unless you explicitly reload the filter.
(AFAIK, the "* modified" change only affected the Image Converter, in 13.7.5; I think the Find panel already worked that way.)