Dropped items can be picked up by players, as can be seen from the screenshots. They can also be picked up by hoppers.
Shot arrows can be picked up by players, also demonstrated in the screenshots. However, for some reason, hoppers cannot do literally the exact same thing.
This also affects tridents.
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Also affects hopper minecarts and yes also affects tridents.
Can confirm in 21w03a.
Can confirm in 21w05b.
Can confirm in 21w06a.
Can confirm in 21w07a.
Can confirm in 21w08b. Video attached.
Can confirm in 21w11a.
Can confirm in 21w16a.
Can confirm in 1.17.
Can confirm in 1.17.1.

Relates to MC-270193
Hi there!
I can confirm, but sounds like a feature request to me.