I have the ode with SSP MP burr and am getting 3:45 - 4min brews with 15g doses and the bed looks quite muddy. The burrs are very well aligned and I'm grinding at 6 on the dial, so I'm not sure if this is just a seasoning issue? The brews have a lot of clarity but there's an underlying bitterness and some astringency. I've run about 1.75kg of a dark roast at a grind size of 7. I've attached an image of the bed below. Any help would be great.

A lot of the times fines can be an issue of the coffee bean and not the burrs. Try other beans from other roasters. I have coffee that my SSP MP puts out a noticeable bump in fines than with another coffee there's a lot fewer fines and I need to grind slightly finer.

For what it's worth (because it may have been all in my head), for the first couple weeks after getting my ode with ssp I thought my cups tasted a bit muddled and saw a lot of fines compared to my previous hand grinder, and that was after seasoning with almost 2kg. After a couple weeks daily use though I do like the cups I get. Maybe I just was finding my way around the new settings or maybe I was just getting used to the new tastes, but your observation resonated with my first impressions

There's some reasonable evidence to support that similar burrs' distribution changes over 10 kg.

I've definitely noticed with my SSP MP burrs that there are more fines than I had anticipated. However comparing to similar grind sizes on a commandante I've found that it appears similar if not more uniform (perhaps expected given the flat vs conical burrs). Do your brews taste good despite the fines? As others have noted, greater amounts of agitation to your bed produce more turbulence which can displace fines adhered to the coffee. Overall a muddy bed isn't necessarily indicative that the coffee will taste bad/overextracted, it's more of a general guideline for understanding if you may want to move your grind size finer or coarser, but ultimately if the coffee tastes good its not important. I also think that the importance of certain rules of pourover (bed should look like wet sand, coffee bed should be perfectly flat, trying to meet exact drawdown times, etc.) may be more relevant for dialing in more entry to mid level grinders where fines are a significant issue that need to compensated for. When you start getting into more unimodal flat burr grinders I think that you start to break these rules and go more by the characteristics of the specific bean, processing method, and ultimately whatever you find makes a good cup.