Google uses a series of smaller flat maps to navigate from location to location.
Evidence?
https://gis.utah.gov/nad83-and-webmercator-projections/
You keep quoting this as evidence. It isn't. Your interpretation of the article does not agree with mine - sorry.
NAD83 is a geographic (globe based, lat/long) coordinate system. It is more accurate for local use in North America than WGS84. WGS84 is a better choice for global use, hence why it's used for GPS. If you want really accurate maps for North America, NAD83 is what you start with.
As the article states:
The advantage of the NAD83 datum is more accuracy for modeling and analyzing locational data in North America.
Note carefully - this is specifically referring to the (geographic i.e. 3D) NAD83 datum,
not a 2D projection from it.
The article then goes on to talk about UTM NAD83 Zone 12N. This is a
projected coordinate (i.e. 3D to 2D) system (based upon NAD83), so you can print it out, add a scale in miles or km or whatever and take it with you. However it is a still a projection and as such it can only be considered accurate for the area (i.e the zone) it is designed to cover (that's why UTM has zones).
it’s the best projection system for measuring distance and area when working with statewide GIS data
It is also nice because it does a great job of preserving the shape of real world objects modeled in your GIS
If the earth is flat and these particular flat maps are the most accurate possible representations, why the need for the phrase "preserving the shape of real world objects" do you think?