Well, truthfully, who is to say that the jersey clip or the bat shard is actually from the player presented on the card? Relics can always be questionable, and one has to have a leap of faith that the company is being honest. Unless one sees someone cut up the jersey, or the player write the autograph, etc, we all have to take their word for it if one is into those things.
Regarding dirt, there was a Fenway Park dirt relic in the 2001 Fleer 100th Anniversary set. I'm carelessly interested, even if for all I know they just grabbed some dirt next to a tree off Comm Ave and put it in a card.