Those are the rules from the Clinton impeachment. But the Senate has to adopt or write whatever rules it will use in the upcoming trial. The Democrats are advocating that these same rules be adopted for Trump's impeachment. McConnell has not agreed. McConnell can just support a motion to dismiss or adopt rules that allow no additional witnesses to be called - provided he can get 51 votes to do so. Had Pelosi simply sent the Bill of Impeachment to the Senate it is likely that McConnell would have been able to get the 51 votes. Withholding the Bill of Impeachment provides time for pressure to be brought on individual senators to support adoption of fair rules of procedure for the trial.

"It is not necessary to have hope in order to persevere."

from the just-like-Watergate NORMS and CONVENTIONS corner of the twitterverse:

But so far @realdonaldTrump has not been impeached for his indictable crimes. Once that happens, he can not be pardoned.
It's probably why Pelosi is holding that over his head right now and talking about impeaching him for obstruction of justice as laid out in The Mueller Report.

— Cheri Jacobus (@CheriJacobus) December 30, 2019

hmmm
President Ford Pardons Richard Nixon
"A month after taking office, President Gerald Ford, addressed the nation on television [A/V, transcript] to announce that he had decided to pardon Richard Nixon."
BONUS!: Full Text of the Pardon Proclamation"

reference
Ex parte Garland, 71 U.S. 4 Wall. 333 333 (1866)
enemies of the state, excluding impeached officers of the state
CRS, "An Overview of the Presidential Pardoning Power"
Miscellany: Always read the footnotes.