It is a great addition to also feeding hay as it adds some variety.  But since they hay is already broken down so much from being chopped and formed into cubes it does not provide the same benefit of making the bunnies teeth and gut work like regular hay would.  So it should not replace hay.  I give timothy cubes to my buns ocassionally and hay cubes are often used in bunny toys as a healthy way to make a “treat toy” that a bunny can consume all of the edible part of the toy at one time without getting too much sugar (as dried fruit would not be suitable).

I get timothy hay cubes as a treat for my pair and they like them well enough, but they’ll nibble them for a little bit and then stop. I think they get bored. They much prefer regular hay, maybe because it’s fresher and softer?

I don’t think I understand what you are asking about. I get Oxbow Timothy CUBES as treats… they are small, compact cubes of dried hay, about 1-2 inches square. They are sold in 1 pound bags, but I believe you can order them in larger amounts from Oxbow.

EDITED:  Okay, I just noticed you had listed a link.  I didn’t see it previously. 

This is what you are asking about:

Yes, I stand by my statement that hay “cakes” (also known as hay “cubes”) should only be used as a treat and cannot be substituted for real hay.  For one bunny, you could give a few a day, as long as the hay cubes don’t prevent him from eating his regular hay.