So I'm still not sure this is a dependency on SIMD (minified code and yada yada.), but they are things where you need Chrome Origin Trials to make the site work as expected with a Chrome User Agent. So it's not as simple as faking the UA to test.
Bug 1703668 Comment 4 Edit History
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So I'm still not sure this is a dependency on SIMD (minified code and yada yada.), but there are things where you need Chrome Origin Trials to make the site work as expected with a Chrome User Agent. So it's not as simple as faking the UA to test.