[anextio]

Malicious compliance?

The EU DMA says they have to allow third party browser engines access to the same resources (the JIT) that Safari has. It specifically allows them to place reasonable requirements on those third party alternatives:

> The gatekeeper shall not be prevented from taking, to the extent that they are strictly necessary and proportionate, measures to ensure that third-party software applications or software application stores do not endanger the integrity of the hardware or operating system provided by the gatekeeper, provided that such measures are duly justified by the gatekeeper.

Access to rwx memory is inherently dangerous, and it's completely reasonable to expect third parties to have proven that they are serious about producing a usable browser engine before putting such a risky product on the market for consumers to download. The law does not require them to allow any third party application to access the JIT, only a third party application that competes with Safari (a usable web browser).

[impossiblefork]

Yes, but that doesn't require rendering performance or anything like that, but absence of security problems.

You can't justify a requirement for a minimum level of performance or some capability. You can justify a requirement of a guaranteed absence of security bugs, provided that that's a standard you impose on yourself throughout the system.