Yaarel
🇮🇱 🇺🇦 He-Mage
This has more to do with the difference between psionic classes. One class has class features that are psionic, like the Psi Warrior. An other class manifests spells by means of ability checks, maybe actual skill checks. An other class manifiests spells by means of spell slots, like the Psion. The class decides the mechancis, not the source.I don't think a Psionicist should pick Psionic spells the same way other Magic wielders do so.
The same is true for any source. A Barbarian might be Primal without any spell casting mechanic.