I don't understand the premise. If your ISP is not implementing neutrality, then it can prioritize small traffic like pings above large-volume traffic such as d

I don't understand the premise. If your ISP is not implementing neutrality, then it can prioritize small traffic like pings above large-volume traffic such as downloads or streaming, so response to a ping says nothing about available throughput, just connection quality. It's like turning on your water tap, getting a drop immediately, then concluding you have the maximum possible water pressure for a day's worth of laundry.