Barr's letter is very narrowly written, Natsku. As one would expect for any legal decision.
Generally speaking, to obtain and sustain an obstruction conviction, the government would need to prove beyond a reasonable doubt that a person, acting with corrupt intent, engaged in obstructive conduct with a sufficient nexus to a pending or contemplated proceeding. In cataloguing the President’s actions […], the report indentifies no actions that, in our judgment, constitute obstructive conduct, had a nexus to a pending or contemplated proceeding, and were done with corrupt intent, each of which, under the Department’s principles of federal prosecution guiding charging decisions, would need to be proven beyond a reasonable doubt to establish an obstruction-of-justice offence.