If it helps one thing I notice in the doco
words: (the default) treats the search string as a list of tokens separated by whitespace, and matches if all of the tokens appear in the string (regardless of ordering and whether there is other text in between)
Part of the problem is “search string” is somewhat ambiguous because it is unclear if it is the parameters you give to search for, or the string(s) that come from this that are tested for in tiddlers.
Perhaps we could use the “search parameters”
words: (the default) treats the search parameter as a list of tokens separated by whitespace, and matches if all of the tokens appear (regardless of ordering and whether there is other text in between)