Speed test not showing correct speed

Yes they are accurate . Within the constraints of that they are testing. A speed test will give you the speed of the slowest part of the connection between you and the test site.

Speedtest measures the speed between your device and a test server, using your device’s internet connection. Several factors involved in the test can result in unexpected speeds . Devices (phones, tablets, PCs, etc…) can have very different Wi-Fi and cellular radio capabilities.

Ookla provides a reliable, consistent test experience across devices . Speedtest provides an accurate, consistent test experience that consumers trust across the many device types available on today’s market.12 May 2021

Considering how well the company is popular and supports more platforms, Speedtest tests can be regarded as a wee bit more reliable than that of Fast . Also, Fast comes across as less transparent about how it conducts the speed tests and its server locations.