With legislation, it is reasonable to extend debate if enough of a minority feel that they didn't have sufficient time to make their case. With advice and consent, the President is asking the Senate for their advice and consent. It is unconstitutional for a Senator from New York to prevent a Senator from Texas from advising the President, and then consenting or withholding consent.
That is the crux of the unconstitutional filibuster -- a minority of Senators is preventing other Senators from advising the President.
-PJ