5 is intentional. Websites choose what size ads are displayed, they plan ad placement and page layout around that. If the page is jumping around as ads load they want it to. They want you to accidentally click, because that gets them more money than simply displaying the ad.
No that was true 10-20 years ago, prior to the online advertising systems becoming so refined. They used to just send an ad with a general size, horizontal, vertical, etc.
It's too common and stick website designs take advertising sizes and loading into account now, so despite constant complaints now it has to be intentional.