A question and then some observations.

I've tried to search but can't seem to find an answer to why there is so much focus on the EK43. It doesn't seem to be the size of the burrs, there are plenty of bag grinders with larger burrs. Is it the way the burr teeth are cut? The Mazzer Major clearly has large flat burrs but appears to produce classic bimodal espresso grin distribution. Is the EK43 significantly different to other large bag grinders such as the Dittings or even the other Mahlkonigs?

I recently acquired a third-hand Ditting KFA903. I had intended to use this for cupping roasts, but I decided to try the Ditting for espresso service. I've really been enjoying it, the espresso has been sweet with less bitterness than the large conical that I otherwise have on the bench. The recipients of milk-based coffee drinks have commented on lower bitterness and increased smoothness. The observations I have regarding the Ditting are that it requires more work to dial in grind fineness than the conical in terms of equalising flow rates, but conversely I've also found that espresso shots maintain excellent flavour even when flow rates are slower or faster than ideal. Notably very slow extractions don't exhibit anywhere near the same levels of bitterness that would come out of the conical at the same flow rate. So flavour remains great whilst mouthfeel and texture varies.

I'm also interested to understand whether the results coming out of the EK43 would be significantly different from what's emerging from the Ditting.

Very interesting questions. I hope someone who has good burr knowledge chimes in

I know that people have used Dittings for espresso before, with supposedly good results. And I know that Mahlkonig is using a Ditting-derived burrset for the PEAK. So there are probably numerous bulk grinders that can produce good espresso. For an espresso grinder, you just need a combination of a sufficiently small minimum modal grind size and a sufficiently large amount of fines (and/or possibly boulders) to reduce flow rates under pressure. With a sufficiently minimum modal particle size, you can produce less in the way of fines and boulders and still get desired flow rates. As far as minimum particle size, it comes down to tolerances. Not all grinders are well-enough aligned to produce a miniscule grind size. Ideally, for modal espresso, you want a really, really small minimum size with few fines and boulders, that way you can adjust grind size without adjusting fines production.

There are a few advantages of the EK. The burrs are really large and may or may not produce a more modal peak than other grinders. There's near-zero retention. It's really fast. It also so happens that Perger is an ambassador for MK - not that he doesn't believe in the EK, just that he'll tend to prefer and experiment with MK products.