8.5.2 says it is ‘in addition to’ 8.5.1.
So you always have to go at least at walking pace, and pick up the disc as soon as you get to it, as per 8.5.1. But, if you were for example right at the other end of the field, there is an ADDITIONAL requirement in 8.5.2 to do it within 10 or 20 seconds (which might mean going quite a bit faster than walking pace).
You can never stand over the disc like that.
But you also can’t just start the stall count as a defender – see rule 8.5.3 and 8.5.4
Cheers,
Benji