Aprobe or even a full pen test is often a precursor to which phase in the attacker "kill chain" process?

The answer is "in delivery phase".

In military speech, an "kill chain" is a stage based model to portray the phases of an assault, which likewise educates approaches to avoid such assaults. The nearer to the start of the execute chain an assault can be halted, the better. The less data an assailant has, for example, the less likely another person can utilize that data to finish the assault later. 
The digital kill chain is a comparative thought, which was advanced by Lockheed Martin, where the stages of a targeted assault are portrayed. In like manner, they can be utilized for assurance of an association's system. check the attachment for the stages.