Please note that it may be missleading to say that the unknown results are treated as 'false' becaues if I change the selection condition to:

where duration in days of E\.period < 120

the same entries will be "effectively treated" as the entries with the period \>= 120\.

Existing Wording:

For the purposes of evaluating a filter, only elements where the condition evaluates to true are included in the result, effectively treating the unknown results as false.

Proposed Wording:

For the purposes of evaluating a filter, only elements where the condition evaluates to true are included in the result, effectively ignoring the entries for which the logical expression evaluates to null\.