Similarity Threshold Indicates how similar two values need to be in order to match. The minimum value of 0.00 causes all values to match each other. The maximum value of 1.00 only allows exact matches. The default value is 0.80.
Can you explain the highlighted text in red as this doesn't actually work. Is it a bug in Power Query or a documenation mistake?
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.