Yes, would have significantly reduced the impact had a train been coming the opposite direction...Are they though? The main line was still fouled.
The timings are consistent with having crossed at Ardlui instead of Crianlarich.Which, looking at RTT, seems to only happen once per day - being the train you've identified as running half an hour late.
Seems to have been resolved remarkably quickly. The Oban and Mallaig portions at 1015 and 1021 left about half an hour late, but two hopur later the 1233 to Oban left only six minutes late (and it had already picked up most of that delay an hour before)
Or are all services able to use the up loop?
Where is the errant 66 now?