No, I get the same.

My understanding is that the “Purge Temporary Files” tool is a part of the program, not the workspace. So clicking that button would be the same as going to the FME temp folder location and just deleting all it’s contents.

Correct, it’s a global setting that purges all of FME Forms temporary files

A workaround I sometimes use when I don’t want to lose all partial run results is to manually rerun the Reader, and if necessary “dirty” the first transformer(s) that are connected to the Reader by making a temporary change to them, running them, and then switching them back to their original parameter settings.  This causes all the Transformer workflow from the updated Reader to become stale, but leaves any other non-dependent Transformer results alone.

A supplementary strategy to this is that if it is just one Feature Type in several Feature Types within the Reader, to speed up rerunning the single Feature Type read is to temporarily disable all the Feature Types in the Reader, then just manually enable the Feature Type(s) that need re-reading, and then setting all the Feature Types in the Reader to enabled afterwards.  I do this if say my Reader is reading millions of features and the Feature Type I need re-read is maybe only a very small number of features and I don’t want to sit around waiting for all the other millions of Features to be re-read at the same time when I just need that one small set of Features refreshed into the workspace.

Have you tried “Rerun Entire Workspace” after updating the reader?