Due to the inert pair effect in the heavier group 13 elements, the +1 oxidation state is much more stable than the +3 state for Thallium (Tl). As a result, $Tl^{3+}$ has a strong tendency to accept electrons and get reduced to $Tl^+$, making it a strong oxidising agent, not a reducing agent. Therefore, the statement claiming '$Tl^{3+}$ is a better reducing agent than $Tl^+$' is completely incorrect. Furthermore, $Al^{3+}$ is much more stable than $Al^+$, making $Al^+$ unstable in solution, and Tl is more readily oxidized to $Tl^+$ than to $Tl^{3+}$ given their standard reduction potential values.