OP was saying about devs needing to build their product/applications/websites on underpowered hardware, presumably as a way to have the same experience as most people. That's reasonable, provided that this is the context where people will use your product/application/website. The context you are giving (slow phones on spotty connections) is so specific that becomes irrelevant for any project manager that could be interested in evaluating the merits of the claim.

So, yeah, I don't know why you seem so upset about my question, but if you detach yourself from the case, you'd see that your response to "are slow phones really an issue?" does not make a strong argument.