The bug
If an arrow is shot into a player and ends up through their main hand, said arrow will not actually be visible from a first person perspective.
MC-136841
Arrows stuck in a player's arm do not render in first person view
Open
15
(Unassigned)
Confirmed
Rendering
embedded-sharp-objects, first-person-arm
Minecraft 1.13.1, Minecraft 1.13.2-pre1, Minecraft 1.13.2-pre2, Minecraft 1.13.2, Minecraft 18w43b, ..., 21w20a, 1.17 Pre-release 1, 1.17.1, 1.20.4, 23w51b
Retrieved
I think this is WAI. The first-person view doesn't accurately represent the player anyway. If it did, then you'd see your legs when you looked down and you wouldn't be constantly holding your arm out in front of you.