Notes of Advisory Committee on Proposed Rules
"If the
hearsay consisted of a simple statement by the witness,
e.g. a dying declaration or
a declaration against interest, ..."
https://www.law.cornell.edu/rules/fre/rule_806
They are allowing people to testify as to what the President said. They are claiming he made admissions/statements/declarations against his own interests.
That is hearsay testimony.
The first and most important exception to the Hearsay Rule is the Party Admission Rule. This is when the statement being offered in Court is a statement of one of the parties in a lawsuit and the statement is adverse to the party who said the statement. For example, party A and party B are in a car accident. On the scene party B tells Witness W that he was talking on his cell phone and was distracted when he hit Party A. W then testifies in Court the statement made by Party B. Technically, this is a hearsay statement and is inadmissible. However, under the Party Admission Rule, the statement would be admissible in Court. The reasoning behind this rule is that people are accountable for what they say and evidence of a statement contrary to their own position is thought to be admissible.
https://hubpages.com/education/Understanding-Hearsay-Evidence