Thanks for thinking out loud -- or rather in cyberspace -- about what could be going on here.

If we were encountering fossils, how would we know? How would we be certain that the "worms" aren't fossils?

But there is more to it. The layering everywhere investigated so far is showing lines of little beads making up the edges of the layers. But when the matrix is ground, no layers show behind this surface. Is the layering primary, then, or is it an erosional phenomenon? If it is primary, why don't we see discreet layers in the RAT ground surfaces? If it is erosional, how does this erosion take place? Sandblasting doesn't make such exquisite beaded edges. Does it?

The notion that the original deposit could have been dunal is interesting. All over Mars, there are light colored dunes, often quite bright, very skinny, and apparently lithified. They sometimes appear at right angles to cliff-faces. There has been some speculation that these light colored dunes aren't
real dunes at all but are erosional remnants of formerly larger deposits. (Of course, how those deposits originated is a mystery~!) Yet, why couldn't the original deposits have been bigger dunes?

But of what material(s)?

Chocolate dissolved in snow? Bright sun-shiney day?

Cheers, BRFelix