UMLR — The included use case is always required for the including use case to execute correctly

In the 'Descriiption' section of chapter '16.3.5 Include (from UseCases)' there is a sentence:
'Note that the included use case is not optional, and is always required for the including use case to execute correctly.'

Interpretation of ‘include’ relationship, implying that it’s usage is valid only if included UC is obligatory for including UC to execute correctly,
is probably the source of opinion, that the only way to model conditional parts of UC scenario using external UC, is by using ‘extend’ relationship.

I find such conclusion in many books dealing with analysis/UML, for instance: ' Business Analysis’, page 188 (ISBN-10: 1906124612,ISBN-13: 978-1906124618).

As a result the difference in aplicability between ‘include’ and ‘extend’ relationship is stressed almost only based on conditionallity of relationship between UC.

In my opinion it’s valid to use ‘include’ relationship when pointing to another UC, that won’t be executed every time the base UC does.
It’s just the internal logic of base UC scenario, that decides if it’s appropriate to call external UC or not.
And if we depend only on result of an external UC, we should use ‘include’ relationship (so most of the time), while when there is a need to introduce its logic we should use ‘extend’ relationship.

I think, that the sentencje:
'Note that the included use case is not optional, and is always required for the including use case to execute correctly'
should be removed or clarified, because if forces analysts to use mostly (if not only) an ‘extend’ relationship, that is far more complicated to use and time consuming to document than ‘include’.