[NTG-context] parallel page streams (pag-str.mkxl)

Dear list, I have this sample: \starttext \input tufte \startoutputstream[es] \dorecurse{25} {\input cervantes-es\par\pushoutputstream} \enableoutputstream[en] \dorecurse{25} {\input zapf\par\pushoutputstream} \disableoutputstream \stopoutputstream \synchronizestreams[en,es] \page \flushoutputstream[en] \page \flushoutputstream[es] \stoptext It is an adaptation from pag-str.mkxl to get parallel texts in facing pages. What I’m afraid I cannot get is exactly facing pages. Am I doing something wrong or is this something still to be added? Many thanks for your help, Pablo