It would arguably be more accurate to compare the actual systems running Postgres and their precompiled binaries. Nearly everything else in a given system running a given version of an application may have an impact on its performance in subtle ways. Its development occurred in conjunction with these other system components, thus it was optimized for them. In addition, distributions tend to ship their binaries with patches not found upstream which can also affect performance. Everything from the kernel and scheduler to glibc and more may affect performance. Newer isn't always faster. Even the containerization you now use might add a subtle penalty that an older non-containered version may not experience.

Basically, it's theoretically possible that some old ass system running version 8 runs it faster than your current system runs version 8 (excluding hardware).

Add to that all the other usual caveats about benchmarks etc (like the fact that IO wasn't tested here but is pretty dang relevant to real world performance)