No it isn't. The Constitution allows the Senate and House to set their own rules. The filibuster does not change the number of votes needed to approve a nominee, just how to get that vote.
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.