Except in this example the CMS /is/ Project X, not part of supporting Project X

And you gave zero requirements for what you need in Project Y

So I have no idea and no way of knowing who looks better. Maybe Project Y just needs a CMS to go with it. Maybe Project Y needs an extremely custom web application with niche needs.

I think you just barely touched on the lunacy of even debating who has the better resume. You need to actually talk to them and understand what their real experiences are. Besides how do we not know that Alice is actually a major contributor to WordPress or optimizes compression algorithms on the side for fun.

Then in that case, Alice will have features A, B, C, and D of Project Z. She won't have wasted time developing a system that didn't need to be developed in the first place.

I guess all this rests on the assumption that Alice did something relevant in all that time she saved. If features A, B, C and D. Basically you seem to assume that each or some of those are relevant software development work and not just more WordPress deployments.

I guess the point is use pre-packaged tools when possible. But somebody has to write new software, so you better get some experience in doing that if you want to be a software developer.