First, I assume you mean Holloway Road which is closer to one side of the
stadium. Drayton Park is closer to the other side. There are entrances and
exits on both sides.

Second, it may be that when the transport arrangements and plans were
originally devised, by people who quite possibly were never going to use them,
they decided upon Finsbury Park for the reasons you've mentioned; but we're
discussing improvised new arrangements by people who want to get to the
stadium by any workable route in difficult circumstances.

Someone travelling by London Overground to Highbury & Islington and
changing there would be ill-advised to chose Finsbury Park instead of Drayton
Park.