Sorry, long day - not following. You saying the whistleblower asserted the summary transcript was "routine and accurate"?
Looking over the statement the only thing even close to what you paraphrase is this:
In the days following the phone call, I learned from multiple U.S. officials that senior White House officials had intervened to “lock down” all records of the phone call, especially the official word-for-word transcript of the call that was produced—as is customary-by the White House Situation Room. This set of actions underscored to me that White House officials understood the gravity of what had transpired in the call.
The reference to word for word might be suspect given the ellipsis - that is pure speculation on my part. Are you thinking of something different?