When you look at a datasheet for a chip antenna, there will always be some mention of a specific reference board. All the parameters (radiation patterns, matching, efficiency) are guaranteed only on this reference board and with this specific antenna placement.

When you place a chip antenna on a different board or in a different location, its performance can change dramatically. In the example video, I simulated 4G LTE chip antenna with the reference board 60x130 mm (top image). Then I placed the antenna on the side of the same board (60x130 mm) and there it was - almost 50% efficiency drop on the lower frequencies!

This is because chip antennas are too small to efficiently radiate by themselves and thus require appropriate ground place size. The optimal location for most chip antennas is in the corner on the shorter side of a PCB, so an antenna can utilize the maximum ground plane.