Actually it won't reset to the default. It will reset to the last value used.
Is there a way to reset it to factory defaults? I know a way to reset all Photoshop's settings to default. But what If I want to reset a single filter?
There's a bit of long term consistency issues between filters and this behavior. (different filters were created at different times over the past 30 years). I've asked engineering to see if it's possible to make these more consistent. Thanks.