This doesn’t seem supported by any data I can find.
“In 2009/10 there were 3,094 gymnasia in Germany, with c. 2,475,000 students (about 28 percent of all precollegiate students during that period)”
https://en.wikipedia.org/wiki/Gymnasium_(Germany)
A similar measure that’s a bit more comparable and easier to find data is rates of tertiary education. https://en.wikipedia.org/wiki/List_of_countries_by_tertiary_...
If you look at the 4-year degree chart, Switzerland’s graduation rate is 49% while Germany’s is 28% for the year 2015. That would be unlikely if Germany’s per-capita attendance for Gymnasium was more than twice that of Switzerland’s.
Not sure where my number come from, honestly the last time I was interest in this was when I was in school.
The OECD, I don't know how it is calculated.
People in the comments call this system harsh, but what they fail to understand is that is not that you get a lane with 10 and that's your lane for ever. In Switzerland you can not go to Gymnasium but if you feel like it after the normal Sek (Secondary School, that is 3 years rather then 6) you can still do a short Gymnasium and get the same degree, its just that you lose 1 year.
You can also do the 3 years in Secondary, then do the Apprenticeship, for example in my case 4 years of school and working in IT (in my case software development) and during that you can complete almost the same degree you get in gymnasium. That degree will allow you to get into 'technical university' and you earn a batchlor. You can also do this degree while working.
Or if you really want to go to a full university like ETH Zürich, you can do 1 extra year of school after.
So the different lanes have a lot of intersections and ways you can go from one to the other. If you are slow at developing you don't go to the gymnasium but you can earn that same degree later in multiple ways if you discover.