The wording of the episode to me seemed to imply that it was the destruction of the Enterprise that caused the loop. If that were the case, it would only make sense for the Bozeman to have encountered this temporal anomaly, been sent to the future, hit the Enterprise and then been looped themselves.
Perhaps their loop starts upon entering the anomaly and ends with the collision. That makes the most sense to me because that would provide the same number of times through the loop for them as the Enterprise which keeps everything balanced. If the ships' destruction is what caused them to enter the loop, then it would require both of them for the loops to even start. The interaction between the ships has to be there. If it is indeed the destruction of the ships that started the loops as it suggests, how could the Bozeman be looping if they hadn't yet hit the Enterprise? It would have to all start with the first collision, necessitating the Bozeman to be pulled forward in time to start their loops concurrently with the Enterprise.
At least that's what I took away from the episode. That, yes, the Bozeman was now displaced 70+ years in time, but not that they had 70+ solid years worth of looping.