The book I have says similar things. The open hearth on the layout is too far away to use the gas from the blast furnaces so I figure I'll use the tankers. That'll add some variety to the rolling stock.
It might be modelers license but it also plays in the narrative that the mills in Youngstown weren't entirely upgraded as the years went along. They lagged behind some. Mary Furnace, in Lowellville, was hand fed all the way into the late 50s. I think it ended life being hand fed. They had an elevator to take the barrows up top. My modelling time period is 1940s-1950s so having outdated equipment/methods works for me. In this case, I'll be saying that the blast furnaces were never upgraded to feed the boilers or open hearths fuel needs.
Thank you everyone for the help!! I appreciate it!