Maxalt, I'm with you on this. I think that the only time you would use the EO Clear prompt was if the FMGC had spuriously detected the EO condition (its criteria for doing so are in the FCOM Vol 4 which we are not given).
Furthermore, if my memory serves me correctly, the early software standards did not include EO predictions so you had to clear it to get any (if a little dodgy) predictions. FMS2 includes EO predictions.
Hope this helps and does not confuse!
Cheers,
mcdhu