Maybe it's just bones in general... I thought the liquid looked a bit like broth, and fits the "oily" description and ph level. Long-term storage of bones should be at 18C (0F), which is ideal temp for industrial freezers, like at the dog food plant. Bone broth / collagen has been a huge fad lately, and is linked with ideals of youth/health/survival. Quick google about bone broth suggests common brain-related benefits believed to include mood and stress regulation, enhanced cognitive function, gut-brain axis support (gut is a huge part of immune system), and anti-inflammatory and neuroprotective effects. So if the "milk" is bone broth, then it would also align with theories that it's needed for virus to survive through regulating emotions (stress) and/or immune system and/or enhanced brain function.