Yes, that's part of it. On desktop with ad blocker on, there is an awful lot of white space: http://imgur.com/jQV5fqy
There is less whitespace if you turn ad blocker off -- it turns out one of the things uBlock Origin is blocking is a social media widget on the left hand side. http://imgur.com/ip093TX
However, that ad in the middle of that screenshot pops in and out of what you are reading as was described by the OP. It's very annoying.
With adblocker on the whitespace is not optimal, but at least the user experience is not terrible.
There is less whitespace if you turn ad blocker off -- it turns out one of the things uBlock Origin is blocking is a social media widget on the left hand side. http://imgur.com/ip093TX
However, that ad in the middle of that screenshot pops in and out of what you are reading as was described by the OP. It's very annoying.
With adblocker on the whitespace is not optimal, but at least the user experience is not terrible.