That's a good argument except it depends on:

(a) one person being able to do the job of the entire YC team.

(b) that person having equivalent relationships with additional capital.

(c) one might make the case that the relationships to capital must be better because ventures are likely to be located further from conventional sources of capital.

50% equity is a lot to give up for two months of effort unless the other co-founder is only expected to put in the initial two months. And if that's the case, why bother?