Not really, this is the damage to your brain that insufficient evidence can cause. Michigan has a storied history of large “Uncommitted” votes in uncontested primaries. For example, “Uncommitted” picked up 16.08% of the vote against Obama in 2012. If anything, this is evidence that support for Biden is stronger that would be expected in Michigan.
Also, you claim it’s evidence that registered Democrats are abandoning Biden; Michigan has an open primary.