The way they describe the Star keeping the samples fresh is with Mystical Mojo, so I imagine that it might supress things such as gene-treatments? Plus who the hell gets a gene-treatment that costs 45K and has an availability of 16F
before they join the Military!? And why the hell would the Military then accept you when you have an obviously highly illegal Gene treatment in you?
Genewipe: This treatment is a major genetherapeutic procedure
that inserts a tag into the body’s neurotransmitters that triggers
accelerated cell death whenever these cease to receive regular neurochemical
signals from the body—causing epithelial cells and hair
to decompose more rapidly when they are removed from the body.
As a consequence, biological trace evidence left by characters with
this treatment irrevocably deteriorates after five minutes (rendering
it useless for genetic profiling or ritual samples).
I guess it depends on how you define Trace Evidence. Examples of typical trace evidence in criminal cases include fingerprints, hairs, cosmetics, plant fibers, mineral fibers, synthetic fibers, glass, paint chips, soils, botanical materials, gunshot residue, explosives residue, and volatile hydrocarbons (arson evidence) says Google. I would not consider things like Bone Marrow Trace Evidence, would you?
I agree that some of the Corps might say they would give you your samples back when you leave, but honestly when do the Corps ever tell the truth to the plebs? Especially a certain Corp whose name rhymes with Cosmetology. And plus the Corps basically make their own laws, whats to stop them from putting in a little clause that no-one knows about that renders certain contract points void?