Why does the Iphone XS on sites with a lot of photos scroll terribly when you rotate the screen?

Question

iPhone

Faced such a problem. On sites where there are a lot of photos, when viewing on iphone XS, you look at one block with a photo, turn the screen to landscape orientation - and you are already on a completely different block. Flip back - and you're even lower. And so you can scroll to the end of the screen.
Example:
https://account.microsoft.com/account/Account?dest...
https://www.symantec.com
I am building a website and I have the same problem.
Tell me, pliz, why and how to deal with it. The ideal convenience of using the site on this device is of fundamental importance to the customer