I'm in a 3 year pure math BSc in Europe, currently on my 5th semester, definitely can graduate by the end of the spring semester of 2022. I have heard in this SE that graduating earlier than planned (for example in 3 years in the US) is only impressive to yourself, but what about intentionally delaying my graduation, would it be detrimental for grad school considerations?
What I mean is fulfilling all requirements of graduation (all mandatory subjects, credit requirements, thesis) without "clicking the I graduated! button". I have not checked the technical details about this, as it would require talking to my coordinator/advisor and I'm still in the exploratory phase about this idea.
My (probably very very dumb) reasoning is that I want to retake some very important classes, real analysis, ODE, differential geometry. I also realized that I want to take measure theory which is only offered in the fall semester.
If I were to do this, I might extend by a semester..., maybe two since most programs start in fall anyway.