This is a poor headline. This isn't for "website purchases" — Epic can support purchases on their own website and not pay a dime, just as Netflix, Amazon, and countless other sites do today. Epic would pay a commission only if they request a StoreKit Purchase Link Entitlement in order to complete App Store-initiated purchases themselves.
Note that Epic's own "App Store", Fab, is now less open than Apple's in this regard.
At this point it has nothing to do with user experience, security or whatever convenient excuses they had. Apple is just flexing how much control they have over everything on their platform.
When did the fee ever have anything to do with those things? Not sure which argument logic trap that is but I’m sure somebody can correct me :) It is their platform, they can charge what they want. Epic is going to charge as much as they possibly can on their platform. If you make a platform that people want to use, charge as much as you like.
Note that Epic's own "App Store", Fab, is now less open than Apple's in this regard.