Eliud is focused on himself.
I actually agree with this. The OP is very focused on Kipchoge's words in the literal sense: if he wants a PB but not the WR, that must mean he's aiming for that small 8-second window, which is ridiculous etc. etc.
But I suspect the comments simply reflect Kipchoge's general mindset rather than a specific literal calculation of his desired finishing time. If you read Jon Gault's preview of the race, Kipchoge's agent talks about how good Kipchoge is at focusing on the things he can change and not worrying about other things. I'm guessing that translates into HOW he thinks about goals. In this case, saying "I'm going for a PB" and "I'm going for a WR" are essentially the same thing in a practical sense, but his choice to talk about a PB reflects his internal focus. Telling yourself "I want to do slightly better than what I've already done before" seems more manageable than telling yourself "I want to do better than any human has done before." Sounds like mental games? Sure, but that's what the late miles of a marathon are all about.