I see. Yeah, PAR3 tries to address the 'lots of files' scenario better than PAR2.

But updates are problematic. You could 'delete' parts of a recovery file if the data is present. However a file being updated typically means that the original data (before the update) is no longer present, meaning you can't really 'delete' that part of the recovery to replace it with the new data. You could try and retrieve the old data by recovering it, but at this point, it may just be easier to recreate the entire PAR set again.

If it's just adding to the recovery set, PAR3 does have provision for that.