It's simple - Elders and HLC members give advice on lifesaving medical procedures using blood. Quite a complex subject, to dabble into hematology with no formal training - I think you'd agree?
But how many elders who go around giving talks, presenting themselves as "first responders" as it were when a medical situation (w/ blood) arises, would even know the basics of first aid?
Bottom line - few if any any elders or hlc members have any medical training. Yet they are in a position (thanks to WT) to give guidance on some extremely complex medical procedures, involving life or death.
I mean ask yourself this: You're a JW and your baby isn't breathing, who do you go to or call? most of the time, trained medical personnel - right. Would anybody really call the elders? Now if your baby isn't healing from cuts and scrapes and the blood issue comes up - now you call the elders? The ones that likely couldn't even resuscitate your child ... they're going to be the ones that give you medical advice on even more complex matters???
If WT wants elders to give any medical advice - they should be medically trained. period. But most HLC members don't even have basic medical training - first aid? nope. CPR? Nope. Hematology? Why yes, I'm an expert - how can I help?