People repeat this a lot, but ironically, it's been pointed out that Apple segregates their hardware and software teams, in order to keep projects secrect. For example, iPhone hardware engineers were not allowed to see any iOS work.
It was recently revealed that breaking down such internal walls was one of Jon Ive's desires.
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As for other major phone manufacturers, they usually have a team dedicated to optimizing drivers for their particular hardware, so the saying applies to a lot of companies, even if using shared main code.
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The upshot is, it'd be nice to know what this test is really supposed to show. There are multiple touchscreen controller chips available, for example, some with very high read rates, and others not so much. So that part is hardware dependent.
The number of touch lines on the screen is also a variable. Perhaps the screen has better touch resolution, but is thereby slower to read fast movement. Etc.
Is this testing the code they wrote, or the OS? Even they noted that the code was a factor.