Let's see what the rule book says.
http://ohsaa.org/Portals/0/Sports/Track-Field/TFmanual.pdf
"The rules as printed in the NFHS Edition 2018 Track and Field Rules Book will apply in all competition involving OHSAA member schools. Exceptions are those noted below or by interpretation in future bulletins."
There are no relevant exceptions noted for our issue, so unless someone else can provide evidence to the contrary, Ohio defers to the NFHS rule book and has no special rule regarding interference. So what does the NFHS rule book say?
Apparently that information must be purchased, which I just did. You're all welcome.
NFHS 2018 Track and Field, XC Rule Book:
Rule 5 Running Events
Section 9 Infractions for all races
Art. 1 ... Interference is any action by a competitor that unfairly changes the course or natural running rhythm of a competitor during a race. This may include bumping, tripping or running across the competitor's path. PENALTY: Disqualification from event.
So it all hinges on whether or not you see the runner in white "unfairly changing the course or natural running rhythm" of the runner in red. That's a really close call, and I see how someone might interpret it that way, but I still say that the runner in red fell on his own and had he not done so, there would not have been a DQ.
If it's my call and I have the luxury of viewing this video, I say no DQ. I also contend that if this strict interpretation of the rule is applied to pack races it will result in the disqualification of several runners from each race. Some reasonable discretion needs to be applied.