Wondering is correct, on the majority of Autopilots Roll & Pitch are the default modes (and not annunciated on Rockwell-Collins APs). On a typical mode without a equivalent alternate axis - Back Course, for example, where there is no Glideslope vertical guidance, most pilots I've flown with will select another source such as Vertical Speed (VS) otherwise the default will be Pitch using the value at selection - effectively giving you Pitch Hold. In either case, the V-bar will still be displayed and give you Roll steering about whatever Pitch value/source you select.