At least in the old days, they'd have to unthrottle everything to get decent speedtest numbers. The cable modems the ISP issued around here had FIFO network buffers capable of buffering 5-10 seconds of traffic.

So, any slow connection would stop the entire household from having decent internet.

I’m suspicious that what they’re saying is true. If so, a simple curl to the site would be all that is needed without running a full speed test.

It’d be great if they could be more methodical and track down what’s really going on. I’d also wouldn’t be surprised to see an ISP doing something like this, but at the same time, it’s much more likely to be networking issues on the consumer’s side than a malicious ISP imho.

I'm not. This would not be the first time ISPs have lied to consumers about their service. https://stopthecap.com/