As described in the subject, AICC total_time accumulation logic differs from that implemented for SCORM tracked activities, mainly due to:
1. the different nature of the 'run time environment', AICC being server side through HTTP POST (HACP) and SCORM, API based, trough a combination of client side logic (JS based) and PHP logic (mainly for storing data, with no logic over the data model);
2. bug MDL-21304 which has hidden the issue.