I think Wikipedia is human data. But to say it's human knowledge (that is, that data is synonymous with knowledge in any context) is actually a pretty hardline epistemological stance to take, one that needs to be carefully examined and justified.
I’d conjecture that the algorithms that do well (as measured by compression ratio) on this particular corpus will also do well on corpuses that contain minimal ‘knowledge’.
Compression algorithms that do well might encode a lot of data about syntax, word triple frequencies, and Wikipedia editorial style, but I really doubt they’ll encode much “knowledge”.
In set notation, what I am saying in above comments is
({data} ∪ {knowledge}) \ ({data} ∩ {knowledge}) ≠ ∅
{data} ∩ {knowledge} = ∅