I read opinions that a coat of sealer before the filler stain, would result in a more clear wood grain. That may be so but the sealer under the stain seems to give a higher variance in the color and tone of the wood grain. It looks uneven.

The other reason for using the sealer before the stain is the claim the stain will muddy the grain. I don't see that at all. At least not in my small sample.