The C100 probably has autofocus because the target market is single operators and people upgrading from DSLRS like the 5D/7D which have autofocus, not "cinema users" wanting to get a cheaper dejikame.
Does the EF model support autofocus? If not, why?
"No. Neither the EOS C300 nor the EOS C300 PL support autofocus. The autofocus needs of a still photographer are very different than that of the cinema user. In cinema use, focus is preferred to be fully manual for full control and smooth shot timing by an experienced focus puller or camera operator."
