This is pretty wild. When you rotate your master password and it re-encrypts everything, that's a perfect opportunity to use a new iteration count. If they didn't want change the value for user's who were at an old default value, they at least could have nagged "your account is using an old/low value for an encryption setting, click here to use the latest recommended default"

Of course, changing it now won't do any good with regard to previous leaks.