But if so they left out the part that would clarify that this was hypothetical, making it look like Trump is just huffing and puffing vainly. That makes the report itself kind of a lie.
It might not even have been phrased as a hypo, but be one in fact. "Who are you going to allow to speak at the convention?" sort of thing.
As for the report being "truthful," that depends on how one defines "truthful." The press is hostile to the Trump candidacy, and the press has no honor or scruples. Sometimes a truthful story pops out, but those are the exception.
Any time I see a quote, I assume it is out of context, and totally misrepresents the truth. That is the case about three quarters of the time.
"If there's no endorsement, then I would not invite them to speak," Mr. Trump said in an interview
The convention has a series of speakers. Some will introduce others, some may invite other to speak on their beahlf. All Trump is saying is that he won't invite these two to speak. That is not the same as saying these two would be totally denied speaking positions at the convention.
The NYT article has no context either. I have no idea how to take the remark, other than speculation on my part.