Why reproducibility is breaking by metadata?

[znavko]

Hello, Guix Help! I am translating Guix manual and found that the author is 
entirely given to reproducibility. It leads to such phrases that metadata 
breaks reproducibility when he describes '--save-provenance' flag of 'guix 
pack' command here:

'This option is not enabled by default because, like timestamps, provenance 
information contributes nothing to the build process. In other words, there is 
an infinity of channel URLs and commit IDs that can lead to the same pack. 
Recording such “silent” metadata in the output thus potentially breaks the 
source-to-binary bitwise reproducibility property. '

I did not expected such a categorical statement. I think, it does not actually 
break reproducibility but only complicates checks. If we have to talk about 
reproducibility to ignoramus, saying 'this option breaks reproducibility 
option' have to have remark 'simply put' or 'plainly'.