That's a little disingenuous, websites absolutely do not always show the same information on devices of every size, let alone 11" vs 13" iPad.
Here's an example of a dutch clothing store, where on the 11" it goes to a mobile-optimised view which only shows two pieces of clothing, compared to a 13" view which shows up to 6 pieces of clothing AND a side bar for filtering on the side.
Note: these screenshots are simulated on my Mac in Safari, but I know this is how the website looks on an 11" and 13" iPad respectively, because I tested it in the store myself. This is approximately how they compare. On this specific website.
Tested in portrait mode, the results might be different in landscape, but I'm not sure about that. Either way I always browse the web in portrait, so landscape results would be irrelevant for me personally.
For those with 11/13" iPads that want to test it for themselves, this is the site:
https://www.debijenkorf.nl/herenmode/broeken