Apple permits "super apps" to host HTML5-based mini-games or mini apps, cloud game-streaming catalogs, chatbots, and retro game emulators — but each mini-experience still has to follow the guidelines individually, be reviewable, and, for emulators, only load legally-sourced game software.
A common cause is an emulator app that ships with or links to ROM files the developer doesn't have distribution rights to, rather than only supporting user-supplied legal content.
"Your app functions as a game emulator that facilitates the distribution of games without appropriate rights, per guideline 4.7."