Indeed these senses are presupposed by listeners according to linguistics theories (Segal et al., 1991;Murray, 1997;Levinson, 2000;Sanders, 2005;Kuperberg et al., 2011).
asr and Demberg (2015) finds that DCs are more often dropped for the discourse relation Chosen alternative (the relation typically signalled by the DC 'instead'), if the context contains negation words, which are identified cues for this relation.