I suspect it is a bias effect. Sometimes, connections are slow for a few minutes: temporary network congestion, maintenance, interference, etc... That's the tim

I suspect it is a bias effect. Sometimes, connections are slow for a few minutes: temporary network congestion, maintenance, interference, etc... That's the time you start to check, and by coincidence, things get better as you are checking. I don't think that your test triggered anything. What is true however is that speed test servers are often located right next to you and maybe given priority access. It means that you can get great numbers despite a poor global connection, but it shouldn't make anything else go better.