Apple's antenna can only be smaller if it's lower gain. I would bet they're making that tradeoff because they don't need as much bandwidth. (Emergency pings could be measured in dozens of bytes, let alone kilobytes or megabytes.)
> antennas with large effective apertures are considered high-gain antennas (or beam antennas), which have relatively small angular beam widths.
You CAN get high gain antennas for things like your WiFi router, it's my goto when an elderly relative complains about their wifi range.
You can't actually increase power with an (inactive) antenna but you CAN change it's radiation pattern. The higher gain omnidirectional antennas just take a radiation pattern that looks like a sphere (0dB gain) and squashes it into a donut shape. So you get more range laterally around the antenna at the expense of less above and below it