JMS originally spoke of both Vorlon-created and natural telepaths, without indicating which were which. But later "canonical" writings strongly suggest that not only are all the telepaths we've seen ultimately Vorlon-created, but that a naturally-occurring sentient telepathic species is almost impossible.
What appears to have happened in nature is that some species developed telepathy at a point prior to acquiring sentience. Since this allowed them to communicate without language and to sense and perhaps even control prey animals without weapons, intelligence never developed among telepathic creatures, anymore than it did among specialized predators like the big cats. Their natural abilities let them thrive in their evolutionary niche - they never had a need to develop tool-making or to organize the efforts of a large number of individuals through language to make up for a lack of individual strength. Only life forms lacking the telepathic gene became intelligent. The Vorlons did not create telepathy, they grafted it onto sentient lifeforms in order to create the weapon they needed. They didn't even come close to perfecting their weapon until about 100 years before the start of the B5 story, when they finally created viable Human telepaths. Before that they'd been down many blind alleys, as Lyta learns in the course of the Telepath War when she visits a very strange planet. (Short story, "The Nautilus Coil" by John Gregory (Psi Corps Trilogy) Keyes.) This notion is also covered in the Psi Corps trilogy.
BTW, I wouldn't dismiss the Lumati as true telepaths. True, they never seemed to make contact with alien minds that we saw, but given their nature, they probably wouldn't. And they may well have privacy laws for "deserving" aliens not unlike Psi Corps's. So once Ivanova was accepted the head Lumati would not read her mind and uncover her deception.
Regards,
Joe