To each their own. I can hardly judge given my ridiculous connection so that I can avoid having to use QoS outside of very basic queuing upstream to assist a couple of devices whose traffic is shaped by their own Internet of p00 SSID shaper. The global network uses WFQ outbound and that's it. Nothing inbound even smashing 8 Gbps iPerfs through. .
Wouldn't the speed test take 30 seconds after which time the other tasks will ramp back up to consume the capacity? TCP constantly probes for capacity, it's what causes the sawtooth on throughput graphs, so once the speed test is done everything should just through the normal TCP congestion detection and mitigation process consume the bandwidth freed up by the speed test pretty quickly?
If the automated speedtest is causing a problem don't run it. Only time I run mine are to annoy my troll and to feed back to the ISP.
If all is working and you've other tasks to do rather than hamstring everything it would seem to make far more sense either shaping the speed test explicitly to lowest priority or, better yet, not running it.