This is fascinating! I have a teenage nephew who is really into lab science. He did an enrichment program this summer where they learned about paraffin embedding; he was telling me all about it.
He told me think about trying to cut a piece of soft bread into think slices with a dull knife. It always gets mushed up (to use the scientific term). But then image trying to cut something firm but not hard, like a soft candle or a chunk of vegetable shortening. Cutting something with a little resistance is much easier and you don't wind up with "mush."