in size yes, but it's capacity is larger than any of the other stands, but that won't last if anfield is redeveloped.
I started looking at this and you could get a few more into the Kop but if it stays around say 13,000 then you're right it will be smaller than at least one of the other stands in capacity unless they reinstate standing. If the Centenary stays the same then you need to share 35,000 between the Main Stand and Anfield Road. Even if they build over Anfield Road to get a decent sized upper tier (3,000 at the moment) I can't see it getting more than 12,000 or so, leaving 20,000+ in a new Main Stand (and possible corner infills).
Those images are awful - I think there's scope for a 55,000 - 60,000 seater Anfield that isn't too unbalanced (like that awful early scheme) with 13,000 Kop, 12,000 Anfield Road, 15,000 Main and Centenary stands.