In a non-trivial way, this means that "telepathy" is defined as something that does not and can not exist. If it exists, it won't be telepathy, because it'll have to be something real, and as such, it won't be "real" telepathy.
If you do give it a concrete definition that permits it to exist, it is often the case that it turns out that we have it in the real world already, unless you define it as some sort of ability to invasively read people's minds or something, in which here's hoping it never exists in this universe.
https://en.m.wikipedia.org/wiki/Closed-world_assumption
A fun question to cut through (or expose) intuitive/cultural heuristics: did atoms exist before they were discovered to exist?
“Magic is just science we don’t yet understand” and all that.
When I understand “sense” in this context I’m understanding “sensor.” A sensor is measuring something.
I think the closest I can get to telepathy without it being a completely wild paradigm shift in understanding is if we could implant technology directly into our brains, thus introducing new sensors.
Why would that matter in the slightest, especially given that their purported abilities all seem to flee to another dimension as soon as they're under scientific evaluation?