The default 'due time' of a task is set to 23:59 by design.
In this perspective, I think it does not make sense to have any task with no "user defined" due time (i.e. with due time defaulted by design to 23:59) being displayed / visible when the filter 'Due by' is set to value 'A) Now' as it is not yet due right now (vitually, I agree, but it is a fact "by design").
However, such a task should well be displayed / visible for value selection of filter 'Due by' of any "higher" setting value like 'B) Today', 'C) Tomorrow', 'D) End of this week', ...
In my opinion, based on this context, I would even consider as a minor display bug that a task with no due time is displayed / visible when the filter 'Due by' is set to the value 'A) Now'.
But I first want to share this opinion in the 'Usage Questions' category (i.e. prior to record it as a bug), to avoid brain storming in the 'Bug Reports' category: so, any comment?