It's a semantic distinction more than anything else. I don't think there are any practical policy differences which would hinge on such variations in nomenclature...
So the campaign was then and this is now, huh?
Either the report is false, although it has been confirmed by another report with anonymous sources, or there is in fact an incoherence in our policy which by the president's own continuous assertions during the campaign concerns a matter essential to winning the war and keeping the country safe.
Candidate Trump was clear, if you cannot properly name and identify the enemy you cannot defeat him. That is not something that can be dodged by calling it semantics, it is important because semantics dictate policy.
What is going on?
It depends of course on the intentions of the speaker. For Leftists looking to excuse and downplay Islamic terrorism, saying that terrorism is not Islamic is a common rhetorical evasion. I do not think that McMaster is a Leftist. I am confident that he is quite capable of recommending hard blows against Muslim terrorists and other enemies of our country.