If a parried projectile misses its target, you can walk over it to pick it up. Like the advancement issue, I believe this is a consequence of the projectiles getting turned into the player's projectiles. Unlike the advancement issue, this actually poses some balance problems as it means you can easily farm tridents from trident drowned by repeatedly parrying them and picking them up. Happens with arrows too.
If a parried projectile misses its target, you can walk over it to pick it up. Like the advancement issue, I believe this is a consequence of the projectiles getting turned into the player's projectiles. Unlike the advancement issue, this actually poses some balance problems as it means you can easily farm tridents from trident drowned by repeatedly parrying them and picking them up. Happens with arrows too.