I can layer concrete up to 7/8ths of a block just fine, but when I try to pour a full block of concrete, whether by layering multiple buckets over a long period of time or by pouring a bucket of concrete into a 1x1 mold, it takes much longer to dry out.

It works just fine when I add rebar, though. Is this intentional?

it should also dry as a full block, I suspect it is due to the full blocks being less likely to tick, I can look into that