Or Firefox Desktop, they don't pass the required headers to enable Firefox's Spectre mitigations in order to use SharedArrayBuffer. I can't tell if Chrome will require it too, because they already do iframes in separate processes.
I believe the general plan is to require the headers in all browsers, for SharedArrayBuffer, including Chrome. (But currently, they work regardless there.)
https://itch.io/t/1028526/cross-origin-policies-for-webassem... itch.io enabled them globally in the past, but it broke some things.