Should packages ipk/bins be reproduceable via sdk?

I'm in the final state of finishing up my docker based package-builder and while trying to verify the results of the windows version and the linux version, i noticed that all compiled packages are slightly different in content and size?

This also happens with the exact same inputs for two consecutive clean runs, only on the linux version? The ipk's and the included bins differ slightly? I tried disabling RELO, but get the same results.
My expectation would be that using docker, i should get exactly the same bins/ipk's or at least for the majority of packages.

So is this normal for packages and what exactly is causing this behavior?

I found this: which would indicate that "maybe" it should be reproducible?