You claimed: we must have it one way or the other. This is false. Game theory says you are wrong and has proofs that you are wrong in the form of proofs of mixed strategies being optimal equilibrium strategies. In these strategies we have the assumption of having it both ways - the probabilities have to add one, but they don't have to be binary.
Lets use a much simpler decision problem to show that you are wrong to not think of things as happening in both ways.
Consider rock paper scissors.
If I want to pick rock, because I'm worried about them picking paper, it doesn't mean I can't be wary of scissors, because I'm worried about them picking rock. For, were I to not be wary of them picking scissors, they could always pick scissors, and therefore, because I had it only one way, I would be exploitable. So now I have to be wary of them picking scissors, but what if I am only wary that they pick scissors? Then I will now play rock. Yet now they can play paper. So what if am I only wary they play paper? Then I must play scissors. Yet if I do, they play rock. So what if I am only wary they play rock? Then I must play paper. Yet now if I do, they can play scissors.
So actually, it isn't that you can't have it both ways, but that you must have it all ways. Anything else and you can't reason properly about the expectations.
> People on HN are always talking badly about companies that don't allow work from home
This is also false. People on Hacker News are not always doing this, they are sometimes doing this, and then sometimes doing other things. There are also many people on Hacker News and each commenter may have a different opinion. Some people on Hacker News prefer working from home. Some people on Hacker News do not prefer working from home.
I feel that you are trying too hard to set up a 'it has to be one way' dichotomy to make your decision problems simpler, but it isn't actually true that making your problems simpler and easier to reason about means that you are doing more correct reasoning. Demanding that others simplify their thinking in a similar way is a request, not for correct thinking, but for use of a time savings technique that you prefer.
Being very clear on that will probably make it more obvious to you that what you are requesting is not as necessary as you seem to think it is: for he calculated his expectation with regard to how exploitable this could make us, then gave you that expectation. This cost you almost nothing to incorporate into your own estimates, so on the whole, it saved you time, at the cost of his time, a cost which you are not paying, but which you benefit from in expectation through correction of the estimates of your faster to calculate yet more exploitable false dichotomy.