Yeah, I agree with what you said but also, idk, I feel like their outward personality is a factor here too. How could a dense Blondie have noticed or considered something romantic was even possible when his friend always looked so serious and deadpan for the most part? It would've been a total different story if he flirted a little bit too but as far as we see, there's nothing.
I guess it didn't help too that they were boss-employee so of course he had to do everything for him. The lines got blurred on whether he was doing things for him out of duty or something more.
But as I said i don't think it's anything to do with him not having noticed. Plus it seems like being that close to someone for 12 years i highly doubt blondie never saw any other sides of the secretary
Idk man 12 years is suchhh a long time it's difficult to even comprehend, i don't think i could get over not even being considered once during that time
Edit: also I think people are missing the point, at least a substantial one, in saying how was blondie meant to know - that's not the issue that he never noticed his feelings - it's what this chap illustrates that from secretary's perspective if you haven't developed any feelings for a person after being that close to them for 12 YEARS (seriously think about how long 12 years is), this request is going to feel INSANE and incredibly horrible to hear. Ofc as third parties we can acknowledge mb blondie genuinely didn't notice after all this time but it doesn't mean secretary can't feel some type of way about what he's just said, let's be so fr rn