No, that's the other part of the rule on Page 67.
Similarly, a Psyker outside a transport cannot target a unit embarked within one.
Do note that this means Psyker powers can
be targeted at the Wave Serpent itself, whether you're outside or inside it. Given the nature of most Psyker powers this is of limited relevance, but it can potentially work miracles with powers like Forewarning, Fire Shield, or in the case of Eldar the ever useful Fortune
Ask not the Eldar a question, for they will give you three answers; all of which are true and horrifying to know.