Even if that were allowed as a solution, it is still a terrible prescreen interview task.

Depending upon whether or not you can use pre-existing frameworks/libraries they are either asking you to: 1) do something which takes so much work that it is completely unreasonable as a prescreen (which will filter out good programmers, who won't deal with that shit), or 2) they are asking you to basically edit some templates on top of some off-the-shelf solution (which will not filter out bad programmers).