Variable derives itself
We say that $\alpha \Rightarrow^* \beta$ if $\beta$ can be derived from $\alpha$ in zero or more steps. (More fancily, $\Rightarrow^*$ is the reflexive-transitive closure of $\Rightarrow$.) In particular, it is always that case that $\alpha \Rightarrow^* \alpha$, for every $\alpha$, due to a derivation of zero steps.

In contrast, in your case it doesn't hold that $T \Rightarrow^+ T$. (This is derivation in one or more steps, or the transitive closure of $\Rightarrow$.)