If 19 games are enough to make a player go from a 3rd liner to a 4th liner, then I assume you consider Tatar an elite player since he's got 20 pts in 22 games?
The players you listed are all top 6 players or great 3rd liners.
Armia and Byron are both average 3rd liners.
In Byron's case, he's underperforming, and in Tatar's case, he's overperforming. Tatar is definitely not an elite player, and his production will come down, while Byron's production will go up. At that very least, thats what makes the most sense with this small sample size.