Yeah, which is why I question their results for cannabis: "Cannabis aqueous extract was prepared by first blending the dried leaves, and then blending the dried leaves in fine powder using a dry blender. The fine powder was thereafter soaked in water for about 12 h and filtered; the substrate was evaporated to dryness, weighed, and then prepared into the mixture of suitable concentrations for the various animal groups".

They also don't appear to have tested this solution for levels of THC, CBD, or anything else. Seems like a pretty poorly designed study. I'm somewhat surprised it even got published.

You can make a tincture by combining cannabis with strong alcohol though.

Is it like cold brew coffee but cannabis and liquor?

Look up "green dragon", it takes ~1 month to make and ends up turning a very pretty florescent green. A single shot gloss of the stuff is very strong, and two shots would be intense even for someone with a high familiarity / tolerance to cannabis.

You're thinking of ice hash.