I never heard of a sensor going off at 1/4 quart low. I have driven many a Sprinter that was lower than that and I never got a warning. What diesel doesn't stay 1/4 qt low, especially one with 300k miles like most of ours. I guess you wait to get an oil light in your personal car before you check that oil as well. You ask was it burning oil or leaking it? LOL That is funny I don't care who you are.
How did they determine the cause was low oil? LOL When they pulled that little stick out of the motor, we call it a dipstick, you call it a waste of time, there was no oil on it and the oil pan did not have a crack in it when the motor let go.