More likely the economics won out. Swing back would save a lot engines but of course that means less parts sold over time.
And probably around 500,000 tons of steel a year.
I send about a ton of old blades to a friends foundry a year .
He thinks I am God because he gets a ton of high quality scrap of known composition for free & that is a big win
I get him to occasionally cast motorcycle parts for me so it is a win win
The swing backs are a different alloy so go into a different drum.
Despite doing 3 times as many swing backs as bars, the swing back drum has only been filled once .
The planet is dieing because we are dong things like making too much steel much of which is not being reused or recycled