I want to push back against this philosophy, that this is a 50-50 call, and so either call is equally justifiable.
INT is a major infraction, with a major penalty: we remove runners from base and award the defense outs. Both runners and outs are precious to the offense, especially outs. The offense gets only a fixed number of those in a game; compared to OBS, with its awards of bases and, possibly, runs, on which there is no limit.
We want INT to be BIG, obvious, and clear to any observer. The best INT calls prompt the runner's coach to yell at HIM, not us. Our officiating philosophy here must be: when in doubt, it is NOT interference. Borderline is not an infraction.
We could debate whether the runner's intent to interfere is really as clear as all that, but it doesn't matter. Even if you think it more likely than not, it's not obvious enough to warrant an INT call. Compare it to the play where the runner reaches out to hit the throw: that's INT.