Trump is the party opponent of the government. Meaning the government could submit out of court statements by Trump.
The government is the party opponent of Trump. Meaning Trump could submit out of court statements made by the government (if that even makes sense).
Trump can’t submit his own statements. Trump’s can only be submitted by his opponent.
Read your link:
However,
Rule 801(d) is an exception that allows for the introduction of hearsay if it is an admission of a party-opponent (e.g., the defendant in a criminal prosecution) and the statement is being offered against that party.
If Trump can submit his own out of court statements to prove something, the government can’t cross examine it and so it can’t be submitted as evidence.