One may draw some conclusions about "full time schedule" based on what OFAC approved prior to 2015 when self certification was permitted for group trips using the "support of the Cuban people", "people to people", "educational", "humanitarian", and "religious" exemptions. Prior to self certification, groups were required to present a detailed schedule of activities to OFAC which was then reviewed and a specific license either issued via hard copy or denied.
It was acknowledged by tour organizers that the "full time schedule" being proposed needed to include all available time in order to be approved. All meals were with the group. The evenings were scheduled as informal group discussions of the days experiences. The group was permitted to attend a music club at night. The schedule basically required that travelers had no time away from the group and leader doing anything that did not relate to the specific OFAC exemption. There certainly was no X hours per day or until 2PM schedules.
In actual practice there were some travelers who slipped away from the "informal group discussions" at night or were out by first daylight to take a walk down the Malecon before 8AM breakfast. But this was never in the schedule presented to OFAC to obtain the license.
Everyone is free a few years later to redefine "full time schedule" but must realize prior to self certification, OFAC required a schedule consisting of every available hour be devoted to the specific exemption in order for the license to be approved.
FWIW: I was on one of these tours in 2009. I have lost the copy of the schedule used to obtain OFAC license but remember it well. I have also had a request for specific license denied by OFAC although for reasons unrelated to "full time schedule"