My take on the affiliation rule is substantially different. I see it more as a protection for the members of the NOMCON.
To have three employees appointed to NOMCON, it is overwhelmingly likely that a company had a large number of people volunteer which means that they have a large number attending IETFs. So either they are an entryist faction (see Sick Puppies / Worldcon) or they are doing a lot of IETF work in which case they likely have a lot of employees being considered for IESG and IAB.
Now consider the case in which the X-co dominated NOMCON chooses the X-co employee over someone else in a contentious position. They are going to be accused of doing it because they are biased. Or maybe they decide not to out of concern that they are accused of bias.
A preponderance of members from one company creates a no win position for all the NOMCON members and it should therefore be avoided.
