Speed test results not very realistic

Running skill gave a wrong speed test compared to the web page. I have a 500/500 internet connection. Skill always returns below that. If I do the test on the web interface I get these results

while doing the test through the skill the results are quite lower

My bet is speedtest isn't grabbing the proper server to do the tests. On the command line utility I could see when I run speedtest without selecting the server, it grabs one based on "ping" (my bet it is grabbing one of the nearer servers, and then making a ping to see the timeout, and not doing a ping to all the servers).
On the following capture I'm showing two random tests using cli

against this location

and this other

against this other location

while if I select my server (I choosed my own's ISP server located on my city)

I know this is a limitation of the speedtest tool, but perhaps would be great to let specify the server to get the most accurate speed test, wouldn't it?

Start with the speedtest CLI invocation and the server-selection path described in the issue. Determine how a server could be specified, then verify that selecting the ISP server produces results closer to the web interface; the issue is done when users can request a specific server for the speed test.