Good Question. I think it's been like that for a long time. I'm not staff so I don't know the full answer. I notice that the search results take up a full page. So there should be a button that takes you to the next page of the search results. There isn't - or if there is, its not visible or obvious.
However if you click on one of the results, you will go to the book and there are 31 of those.
As far as I am aware the only other John Wayne comics would be movie adaptations. Dell did adaptations of about 6 John Wayne movies but I think they were in the 60's and therefore not Public Domain and not on this site.
You could go to GCD - Grand Comic DataBase, which lists everything,
https://www.comics.org and search for John Wayne and then come back here and if there is anything listed before 1960, search by publisher. Here
https://comicbookplus.com/?cid=1507 OK - I just had another look at the search results.
Underneath the last entry there is a small and nearly invisible line of check-boxes, starting with #1.
I have missed this in the past, and I may not have been the only one! So thank you.
Good luck Kate!