A hypothetical that fits your premise: Senate rules that 95 Senators have to agree to vote on ALL matters that come before the Senate. Treaties, budgets, spending bills, etc. Since they rarely get around to meeting this threshold, the Senate rarely votes on these matters. Presidential prerogative and House bills are bottled up due to a Senate rule.
According to the principle you describe, this is Constitutional because the Senate hasn't actually conducted a vote.
According to the Constitution it would be.
I probably didn't make it very clear but I was not
suggesting the Senate rule was unconstitutional - of
course I know they can set their rules - but that the
filibuster applied to an issue that doesn't require a
supermajority IS, the confirmation of judicial nominees.
In fact this rule can be removed by simple majority.