one check
Measure a browser you are not sitting at
The ordinary flow assumes a person in front of the browser being measured: consent, a click, a short pointer task. The browser you actually want to check is usually headless on another machine. This gives you a one-time address to open with it.
The reading is taken on the machine that opens the address, not on this one, and it is stored under a one-time token so you can read it here. Layer 4, how a hand moves and types, will be missing, because there is no hand.
What this one page cannot tell you
How that browser is operated. Layer 4 measures a hand moving and typing, and there is no hand, so it is reported as not available with the reason 'this needs your hand on the device'. Calling it a gap of the browser would be wrong: the same browser would produce it if someone were sitting there.
The interesting part is usually not a single value but the disagreement between two. The full check reads all five layers and shows you where they contradict each other.