being a telepath isn't easy. Being an apprentice one even less. That's why all apprentice telepath first learn and practice on their teachers, then on volunteer from mind reading friendly species, practising the basics, be it reading someone's mind, communicating basically and making the whole thing as less uncomfortable as possible.
The first true "test" is to go and listen as long as possible to a small group of humans passing by the main hall. Officially it's to make sure the basic are learnt, utilizing the relative low telepathic capability of humans to prevent any high backlash.
Unofficially it's to present, or more subject, the apprentices to one of the most chaotic thought process known.
The record for an apprentice is less than 30 seconds. -- Anon Guest
The Melil have lived their entire lives with telepathy. They have not lived their entire lives with other species. As a long-lived people, they have plenty of time to learn acclimatisation to other beings' mental emanations. The Melil are used to restraining their thoughts. Other species are not.
Thus, when a Melil wants to enter into the greater spaces of the Galactic Alliance -which they do owing to complicated fertility reasons- they have to train to be accustomed to what they refer to as Galactic Static. This is thousands of different minds, with different views and ways of thinking, with different ways of viewing the world around them. Most are relatively uncomplicated. A special few are not.
Of all the varied services they could perform, Melil telepathy is most widely useful in the UFTP's eternal search for all of its colonial worlds. The people on the other end of the freshly-opened wormholes definitely do not speak GalStand, have a vastly different culture to the one finding them, and may not be at the same technological level. Things can get complicated fast.