This is true after 4th grade, but 1st through 4th usually have kids learning every regular subject from a single teacher in a single classroom. Of course there are many states and even more school districts, and it's very possible that some of them do it differently.
Looking at the syllabus for my state now (https://www.lehrplanplus.bayern.de/fachlehrplan/grundschule/...), the most advanced world map-related topic in elementary school is something like
Students
- learn how to read scale on a map
- understand where their home is on a map and in which state and country and on which continent it is.
Using their crappy search function, I don't get any results for map projections, Mercator, etc. at all, even further down the road.
(Note: I'm aware that Bavaria is known for being very centered on itself. This might be a large cause for this.)
But I don't think that's the age to learn about map projections. My oldest child just finished first grade though, so I'll keep an eye open.