I'm not 100% on this, but I remember hearing that the 40mm APO-Com-H was designed for enlarging APS-sized negatives, or 1/2-frame negatives. This line of lenses was brought to market in the late 90s, when APS cameras were becoming more popular.
But since it covers the 35mm frame completely, it doubles as a WA 35mm enlarging lens. A friend of mine makes 20x30" enlargements from his 35mm negatives(both color and b/w), and he uses the 40mm to achieve this, using a Durst 4x5 enlarger with a drop table. It helps since he only has 8' ceilings in his apartment, and doesn't have to reach as high up to adjust things vs using a 50mm(or 63mm) lens. He previously used a 63mm El-Nikkor 3.5 for printing, but he wanted to go bigger with his printing. He has now "standardized" on pretty much using the 40mm ACH only.
The 63mm nikkor now sits in a drawer 99% of the time

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thing is though: he said he had to get a recessed lensboard(about 25mm) for his enlarger, so he could use the bellows to focus rather than racking the head up and down
-Dan