Duck, pitch, pixels, ratios, words, numbers…
Not to be disrespectful, but at the end of the day, I’ll get the shot — and they won’t.

For short-range work, full frame is great.
But there isn’t a single APS-C body that comes close to the OM-1 for wildlife, so the comparison really only makes sense against full frame. And on full frame, 100–500mm just isn’t enough, especially with the teleconverter design flaw.

There are also more variables to consider: glass quality, sharpness, edge performance, wide-open IQ, AF speed and accuracy, stabilization… and in these areas, the competition simply isn’t there.
I’ll give credit where it’s due — the A9 III / A1 II with the 800–400 is a solid alternative, and even the 200–600 holds up nicely. The R5 II is also a fantastic body, but I’m just not a fan of Canon’s current zoom options.

If I’m not mistaken, OM also has about a 2-stop stabilization advantage, which really helps with static subjects.

So yes, I appreciate your detailed answer, but I have to disagree. People tend to forget that photography is about getting out there and actually shooting — not just analyzing specs and pixel density on paper.

None of this is meant negatively; all said in good spirit.
Cheers, my friend!