From personal experience, it can happen. At one point, I was personally responsible for about 2 million lines of code. Over several years, I was able to reduce it to about 500k through generous use of code generation for ORM type work. The generated code never ended up in VCS, but the generator and model did. Certainly helped checkout/update times as there was several thousand fewer files to deal with.

I was one of about 900 engineers at a financial company of about 1500 employees at the time.

I don't honestly know how many lines of code there were across the company, but I imagine it easily exceeded 100M. It took us a full week to do a full recompile of everything. We had no CI... Was always a problem approaching release time.