I don't think it's true that he's taking just individual votes for Trump; I think it's total % of Trump votes. If you listen to him at 21:00--
"If you're a Republican, most Republicans probably voted for Trump. Now in some precincts like this one, it looks like 5% more people--which could've been Democrats, Independents or others, even Republicans--voted for Trump"
This leads me to believe he's looking at the pooled % of votes Trump got in total (not just from Individual, non-straight ticket voters).
Also all the plots from Phil Evans are labeled with % Trump votes, not % Trump Votes Among Split-Ticket voters.