It wasn't decided really, I just submitted a patch for review. I think Tom and you can decide. My phone (S23U) reports 5, so I based it on that, but we can change it to 10.
Bug 1826051 Comment 6 Edit History
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It wasn't decided really, I just submitted a patch for review. I think Tom and you can decide. My phone (S23U) reports 5, so I based it on that, but we can change it to 10 (which I think makes more sense assuming some tablets might support 10 fingers)