What might be the reasons for such a tiny tracker?

Just a note: the pictured M3 (world's smallest computer) was introduced in 2015, and remained the smallest computer in 2018.

Is the grain-of-salt sized device shown here a GPS tracker? Yes, and no. Actually, one would need at least 32 of these tiny computers working together. These computers are injectable, and while remaining virtually undetectable, they continually broadcast and upload data about their host. This could include a wide variety of information, from health to location.

Location is determined by nearby wi-fi networks and connected devices, just like your smartphone uses these same networks and devices to fine-tune its location. While this presently covers populated areas, the Internet of Things will make these processes possible just about anywhere.

This question remains: if these tiny computers are only for overt use, why make them so small that they would be nearly impossible to find or remove?

Information for this meme was derived from three articles available on the University of Michigan website:
• Michigan Micro Mote (M3) makes history as the world’s smallest computer - March 18, 2015
• Injectable computers can broadcast from inside the body - June 6, 2016
• Internal computers could help locate missing people - April 19, 2021

There are no GPS trackers as small as indicated.

This is complete bullshit.

Probably made up by a liberal.

Did you Duck it or Google it before deciding "this is complete bullshit"? That's OK. No need to look it up: I have cited my sources for you.

Yea because those liberals are afraid of that sort of shit... I am not aware of any liberal Q cult members. That GPS stuff is full on Q....

Fascinating. Is it a liberal lie or a Q conspiracy? I agree with you that it sounds much more like the latter. But it's just technology, and like anything else, it can be used for good or evil. It raises questions in my mind. I have cited my sources.