Antenna mounting confusion from Datasheet
ok, One possible answer, yet no clear reason, so not really very well solved, but clears some things:

I've now received a comment from one of my colleagues as well that, yes, that's how some of the antennas are mounted.

Even though there's an evident short from feedline to GND due to the chip antenna pad, the internal construction of the antenna would expect such connection via a specific footprint - as if some internal chip antenna structure would require that kind of a footprint.

So yeah, all in all, I probably won't be able to properly mount this on an existing layout, as this specific antenna needs this kind of quirky layout.

But maybe someone else can shine more light on it, why is that mounting so (even when the component looks similar to 0603) ?