This is on CiviCRM 5.36.
I try and create a rule with, say, First Name and Last Name, both having a weight of 10. If I set any Threshold greater than 10 so as to require both to match, I get the error:
Weight Threshold to Consider Contacts 'Matching': 11 Total weight must be greater than or equal to the Weight Threshold.
I first saw this when trying to change the usage on an existing rule which had worked previously.