Has the tiger’s Strength score increased when it has levelled up? Maybe it has an exceptionally poor chance to raise Strength?
Every time a follower gains a level, it has a chance to increase its stats (Strength, Agility, Vitality and Grit). None of these are guaranteed to raise. So it’s entirely possible that your sabertooth still has its starting Strength score.
You can see this by holding down the Interact button to open the interaction wheel and then selecting the Information icon to see your pet’s stats, as well as the chance to raise them.