The fuzzy merge documentation doesn't match observed functionality. The following page (https://support.microsoft.com/en-us/office/create-a-fuzzy-match-power-query-ffdd5082-c0c8-4c8e-a794-bd3962b9064...
Hi lasersharks
These two figures are the results obtained when the Similarity Threshold is equal to 1 and equal to 0. You can see that when the Similarity Threshold is equal to 1, which is an exact match, the result is 1 to 1 (case doesn't count). When it is equal to 0, it is a fuzzy match, which can be one-to-many. This is the difference.
Best Regards,
Community Support Team _ Ailsa Tao