Epic Games, the maker of Fortnite games has challenged Apple for its stand that third-party app stores would compromise the iPhone's security.
In a fresh court filing, Epic said if Apple can allow sideloading on Mac devices and still call those computers secure, then surely it could do the same for iPhone, reports TechCrunch.
"For macOS Apple relies on security measures imposed by the operating system rather than the app store, and 'notarisation' programme that scans apps and then returns them to the developer for distribution," the new filing said.
"The operating system Apple uses in its Mac computers (macOS) does not include the challenged restraints found in the iPhone operating system (iOS), and Apple publicly touts the Mac's security," read the filing.
Apple also permits multiple alternative payment solutions in the App Store for apps selling physical goods, "confirming that the requirement to use Apple's in-app payment solution, IAP, for digital goods serves no pro-competitive goal".
"If Epic prevails, the App Store would not be dismantled. No customer would ever be required to use any of the things Apple complains about an alternative app store, direct downloads for app distribution, or an alternative payment solution. The difference is that Apple would have to compete for its customers," said the Fortnite game maker.
Last year, a US judge ruled in the Epic Games v. Apple district court case that Apple did not have a monopoly in the relevant market.
However, the court in California decided that Apple could not prohibit developers from adding links for alternative payment systems outside of App Store-based systems.
Apple has said that permitting sideloading could risk users' "most sensitive and private information".
"Supporting sideloading through direct downloads and third-party app stores would cripple the privacy and security protections that have made iPhone so secure, and expose users to serious security risks," the company said in a paper.