I don't believe this for a second. I worked at multiple companies that manufactures setup boxes for DVB/IPTV; and basically everyone uses WebKit (regardless of the browser used, most commonly Opera, Netfront or Ekioh) essentially no setup box has more than 512MB RAM (where of about half is reserved for system use- especially MPEG acceleration), there is no swap at all.

Several runs their UI in a web browser, they have a second browser running HbbTV and often the same is used for arbitrary user surfing, there is no known problem with leaks that I ever heard of (atleast not to the extent it causes issues).
The same applies to essentially all "smart tv" etc.