As of today, the Canon Store/USA has some refurbished RF lenses at slightly discounted prices. They come with a full Canon warranty, packaging may be original or not.
I've been mistrusting refurbished items (particularly electronics) ever since a friend of mine in college bought a refurbished TI-86 calculator that ended up being very glitchy and basically unusable. What tends to happen, is the item is returned when the first user discovers something wrong with it, and after running the typical tests the techs may fail to reproduce or catch the problem, as they only get very limited time to work with that item. They assume the item was returned just because the user didn't want it, and there's likely nothing wrong with it. So back into the box and on the shelf it goes to be sold again.
I'd probably pay the extra $200-$300 for the new lens, or go the used route to save more money instead.
When I was shooting Nikon gear, most of my lenses were Nikon refurbs, and I had no issues. However, you have to weigh the savings versus the cost of a new lens. If I'm contemplating a $2500 lens, I'm not so sure that saving a couple of hundred bucks is worth the potential aggravation. On the other hand, I think that electronics and high tech repairs have come a long way since Texas Instruments first few products (my first calculator in engineering school was a Texas Instruments product and so much easier to use than a slide rule).
That's what I'm thinking too. The new lenses from the list in the OP are only two-three hundred more on Amazon, and I would have a month to return them if I'm not satisfied for whatever reason. Refurb stuff really needs to be a lot cheaper to be worth considering.