I don't know the proportions for mortar, but I do know that in the days of old, the mix was quick lime, cement and sand. The quick lime (calcium oxide) would burn you due to its desire to get wet, would be slaked overnight to get it completely wetted. Today, I am sure that the mixes are using hydrated lime, (calcium hydroxide) which will still burn due to high pH. It is the lime that provides the stickiness. The cement provides the strength, so if it bonded, it will be good. I would not be too concerned over the bond to the bottom, but more concerned about getting the vertical steel imbedded, which will provide both shear resistance, like bonded block, and bending resistance from the weight of the water trying to tip the wall over. I am not sure which is the higher stress, but the rebar provides both, once embedded in concrete mix within the voids of the block.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard