As I understand it, calcium chloride is a salt that can burn when ingested which is why, similarly to Kent's liquid calcium, calcium chloride does in fact need to be diluted before adding so the instructions given to you is correct. Calcium chloride is commonly used in saltwater setups and is the primary ingredient of Kent's liquid calcium. Calcium chloride is more soluble than calcium carbonate and apparently does not alter pH much compared to calcium carbonate so if you are trying to make your pH more alkaline, then you'll have to use calcium carbonate instead of calcum chloride.
Someone in another forum tried to add lime. Lime can actually burn as I had used this to negate the smell of chicken manure in my backyard. Her usual routine was dilute but for some reason, she was in a hurry and dump it directly killing her snails in the process. Airing on the side of caution, if it were me, I wouldn't have chosen to use this as I play a big risk in losing some of my snails in the process however much I'd love to for the sake of the snails' healthy shell growth. If the range of calcium enrichment is rather wide, why bother choosing the riskier ones?