Didn't come into play, but...

[TussAgee11]

B/R running to first base within confines of 45 foot lane. F2 throws. B/R is running waving his left arm over into fair territory, not a part of his natural running motion. Ball hits him.

This is clearly interference. Why else is he doing this other to interfere? If I see no explanation as the umpire (loss of balance, some weird way of protecting himself), I have to deem it intentional.

I think in the original situation, we will differ because we call various levels. Inexperienced players, that may not be interference because he may not know any better and his acts aren't done with intent in his own pea brain. D1, why else is he doing that, does he not know how to play baseball?