Durometer of cured sealant

Probably not and depending on how it is measured, may not even accurately determine cure state.

Hardness is probably the most frequently measured property of rubbers and sealants and the durometer the most widely used test instrument. The durometer and the significance of its readings are often criticized on two counts. First is the measured values are unreliable because of mechanical considerations and inconsistent measurement procedures. It is not uncommon to find 5+ point differences in measurements taken by different operators on the same sample. That's one of the reasons for the broad tolerances in the durometer hardness of rubber products, ranging from ± 7 points for hard compounds to ± 20 for soft ones.

Secondly, the characteristic that is measured; surface indentation (or surface resistance to indentation) rarely bears any relation to the ability of a rubber or sealant product to function properly.

Table-top instruments are considered more reliable because they reduce the human error in their application. The ASTM Hardness Tester is often used as a referee method to resolve disputes but even with this tester large tolerances are generally expected.