My father-in-law had a similiar experience here in Canada. In circa
1942 he was an apprentice machinist for a new factory tasked with
manufacturing a British 4.5" naval gun design. IIRC, the original
British procedure for any shaft/bushing was to machine the shaft with
0.020 in interference and the hand file the shaft to fit. As he said,
there wasn't one in a hundred in their labour pool that could do this.
Part of his job was developing new dimensions and tolerances to allow
parts to be manufactured independently, inspected for dimensions, and
then assembled without further machining.