I base "melt" on how the material reacts under heat.........as in does it melt like beeswax..
I'm more familiar with evaluating the melt based on how much residue it leaves behind on the nail.
I use high quality indoor as well and many of my favorite strains are lucky to yield 15% with rosin or solvent extracts. I would only hit full melt sift ever if I was getting 15%.
Are you basing those numbers off nugs? Whole plant? Whats your sift setup/process look like? I've been wanting to get into cryo-sifting.
I don't grow, sift or otherwise make concentrates and have no special knowledge. But, I don't think anyone's numbers are crazy.
https://www.alchimiaweb.com/blogen/bubble-hash-fresh-frozen-vs-dry-flowers/
Keep in mind that @arb is talking about dry sift, bubble hash utilizes all the advantages of a stacked sieve so its easier to separate full melt compared to dry sift, where those plant contaminants are much harder to separate without the water medium. An air jet sieve is the closest I could think of.