All these (ad)ons always take priority over performance.
What you’re linking to is about their proposition of chat control for CSAM scanning, which is a completely separate thing from the Digital Markets Act that will force big Messengers to become interoperable.
you’re actually right. I had merged these 2 in my head because of the other issue that arises from this requirement which will affect the security of the apps, especially in apps that work with e2e encryption. e2e interoperability is kinda impossible to be implemented especially in the current deadlines. You can read more about it here https://www.eff.org/deeplinks/2022/04/eu-digital-markets-acts-interoperability-rule-addresses-important-need-raises