"Time to stop rambling and ask if the ARRL article distinguished the IF
transformers with different part numbers?"

Yes

The first and second stage transformers are designated "456 kc interstage if
transformer, permeability-tuned (Millen 64456)". The third if transformer
(to the diode detector) is designated "456 kc diode transformer,
permeability-tuned (Millen 65454)".

The schematic drawing for all three transformers are the same, but the
secondary of the last transformer would be different to attain a lower
impedance.

73, Colin K7FM