Since I remember such announcement (about 15 month ago), but in German it seems the translation devil is not LHs friend. In German they said by that time, that all US flights will depart from A only. B was never mentioned then and having no extra security screening in B would have never worked per the departure requirements to the US. So this english announcement was and is BS.

Finally with the opening of the new C gates they immediately moved some morning and early afternoon US departures to there. Again announced in German to me (IIRC via email from PPB). Not sure, what the translation devil did then on the webpage.