Actually, the latency due to distance is only around 500ms or so (half second), and that's all four legs of the trip, as the total distance is only ~90,000 miles or so, though the precise distance depends on your location and the location of your gateway (which is always in a different state than your own). The equipment itself ends up taking the total latency up to about 600-650ms on average for geo-sat internet like this. The result of 0.1 seconds on the responsiveness test is a head scratcher, as even if it included only the two legs of the return portion (from the gateway to the satellite to you) it should still be more than double that just from the latency alone. However, whether it's actually supposed to include the latency, and if so, what parts of it, I can't say, as I don't know the test's technical aspects.
To be honest, I don't even know why they have the web responsiveness test anymore, as it was primarily used for the legacy plans on the older satellites, as in the ones with a top speed between 0.5 to 1.5Mbps or so. It also possible that's why you're seeing a result like that, though I can't say for sure.
As a measurement tool, I'd rely more on the testmy.net results than anything else. Fast.com can also give a good result, but it causes the Video Data Saver to kick in, which will limit the download speed result to around 3Mbps or so, as the test mimics streaming, which is what the VDS is designed to help save data with. If the VDS is paused or turned off, Fast.com should show the actual top speed at the time. You can see what I'm referring to here.
