When I had spawning managuense back in the late 80s, in any spawn, there'd be small number of these "spotless" morphs (maybe 4or 5 out of hundreds).
I separated and grew a few out to see how they'd appear as adults , but usually if left with the other fry, and their brothers would and sister cull them.
Back then most aquarists wanted perfect examples of a species, so didn't find these arguably more bland managuense interesting, so I had a hard time unloading them.
Things may be different today.
In any cichlid species it is common to see color variations like these. Its natures way of providing a pathway for the species to continue if some natural disaster happened changing the topography, making the normal color form obvious to predators like birds.
Consider a situation where an earth quake and subsequent flood or other nature occurrence wiped out all cover, such as vegetation, that previously helped camouflage a species like managuense, in this case, a morph the blends in with a barren sand bottom, might have an edge.
Here in Central America earthquakes are common, so such a morph could end up being an important factor in the continuation of a species.
Where I live in Panama, at least 4 measurable shakers have occurred this year so far, none were cataclysmic, but the possibility is always there.