Why is it suggested to keep 2cm between the chip and the remote antenna in TESEO-LIV3F?
that is an exceptionally low-quality section of a manual for such a large and reputable manufacturer. ST should really re-write the manual.
What they probably mean is &quot;if you have an external antenna, you do that, because you want to have an antenna that's better than what you have could mount on the PCB itself. So, don't mount that antenna so close to the PCB that it couples back into the PCB, that would be stupid.

Or, maybe not. The whole chapter is badly written, hand-wavy non-specific anecdotal information.