I believe Pound changed the punctuation purposely.  It was part of the
editing process.  The poem was originally published with gaps between the
words, stressing the rhthym.  This was unnecessary -- the rhthym of the poem
is clear.  He changed the colon to a semicolon because the colon implies
"are like."  The ideogram is works a bit differently than metaphor/simile
and so he substituted the semicolon.  I read an article in a journal a few
years ago regaurding this topic but I've forgotten which one.