Why do the contractors say they can’t recreate it?

The ones that I've heard back from said that's not part of the services they offer. I didn't think it was a particularly unique task, but I haven't found anyone in my area that advertises that they offer faux inlays

You could ask if they could sand down the floor, you tape off where you want the border then they stain it and apply the topcoats

I have done things like that on top of wood dressers.

To do that floor, it's just taking the wood down it's natural state, taping off your design, and applying the stain to that portion of it. Then the entire flooring gets the clear coat. (the other part stays natural)
Is it something you could do? yes, but it's a lot of work. The time consuming part is measuring and taping. takes many, many hours.

This one was actually a floor paint, not a stain, but you would do the stain in the same manner.

There is a link to this one if you're interested in a DIY!

Is it something you'd be willing to pay for? not going to lie, based on the size of the room it could be 1K-3K. is that worth it to you? You would have to call a specialist in wood finishing and borders, not a flooring contractor. Someone who specializes in staining wood borders.

I would think for that price you could have your flooring specialist cut out a ribbon of wood and inlay a darker species in there.

Another option is to prep the same way, but instead of stain use a real milk paint. you could do any color. (need to be on raw wood though). same clear coat application.