Are Sky prevented from just offering their own entertainment channels as an entry point, or at the very least making them available to sports or movies subscribers without needing a general entertainment pack.
I shouldn't have called them packs, they haven't been packs for ages. They're bundles. The packs was the old way of Sky TV.
Sports and Cinema have always been classed on Sky as the premium/add-on channels even back in the days when they had the pick-and-mix choices of six packages on offer. Wiki suggests Sky Sports did use to be available standalone back in the analogue days, but was discounted if you took it with movies. I suspect it became "on top" with Sky Digital.
There is probably nothing to stop Sky selling Sky Sports on its own if they really wanted to. But why would they when a requirement for at least the basic package guarantees at least £20 a month extra on top of the Sky Sports asking price?
And anyway they're throwing deals out again left right and centre - half price to the Cinema channels and free fibre internet as long as you have a Sky Sports subscription are the two current ones.