Edit: The Carnisylvan Sampling's has been removed from bestiary on 20/07/21.
In Library of Carnisylvan Sampling's it say's " Carnisylvan saplings are a sinister spawn, created by vile poisonous carnisylvans as a defense mechanism. They try to overwhelm their victims in number and will explode when close enough to their target. Despite being very small and more plant than human-like when compared to their elders, they can be just as dangerous." 1
I have analysed some videos, and found actually video confirming, that they are created by Poisonous Carnisylvan2. I believe due to their destructive nature running into players and exploding (short lifespan), lots of spells used by mobs and fact they are small, they can be overlooked by players.
a. Itexo Video- CARNISYLVANS HUNT- 1.4 KK PROFIT/H- BEST places to hunt for KNIGHTS
https://www.youtube.com/watch?v=nMVy4-4If68 - Check time: 0:55; 1:22 etc
b. Tibia Bobzerah- TIBIA: Forest of Life - Carnisylvan PARTY HUNT
https://www.youtube.com/watch?v=YcPoFd1BUvk - Check time: 1:14; 1:32 etc
It is strange though that it is not in Prey, neither Task list.
1. https://www.tibia.com/library/?subtopic=creatures&race=carnisylvansapling
2. https://tibia.fandom.com/wiki/Poisonous_Carnisylvan