It is just possible that two separate stereo mix-down tapes were produced in 1965, one being used for the LP and the other - eventually - for the CD. If this were the case then we would not need to guess at who might have remixed the album in 1987. 

However, we've recently learned that the reason the new SACD reissue was remixed (as well as remastered) was that the original stereo master tape was worn out; so - as with Blonde On Blonde - it seems pretty likely that the same reason applied in 1987.