It will work but the question is will it give the results you want. It looks like the round rails are fully supported if so that is a good thing! If not it would be best to use this on a very light duty machine. If you look at the specs the slide just barely passes for what I would consider to be acceptable design forces. I’m on my laptop home at the moment and have already forgotten the specs but I think it was 60 pounds side loading. I’d call that a light to medium duty slide for a router.
People like to knock round rails and there are some megood reasons to do so but at the right price they are far better than many of the cheaper or DIY solutions for linear motion. The slide will work but as I said it depends upon what your expectations are. If it doesn’t meet expectations it will be good enough to machine a replacement out of aluminum. So I really don’t see a reason not to use the slide. If you pay attention to the gantry (y axis) saddle rigid mounting should be easy. It you have concerns make the saddle large enough to accept a larger Z axis in the future. You didn’t mention the going price but I imagine that the leadscrew itself is worth what you paid.