No; there have been a number of (controversial) pardons for people who were either not charged or had not been convicted. Gerald Ford set something of a precede

No; there have been a number of (controversial) pardons for people who were either not charged or had not been convicted. Gerald Ford set something of a precedent by pardoning Richard Nixon for activities related to the Watergate cover-up, and Joe Biden pre-emptively pardoned his whole family. These applications of the pardon power have been controversial, but never successfully challenged.