Despite the rapid adoption of Generative Artificial Intelligence (GenAI), empirical studies comparing educational task performance with and without its assistance remain scarce. This study addresses this gap by examining how in-service teachers draft authentic Self-Regulated Learning (SRL) time-management scenarios with or without GenAI assistance as part of a teacher training program held in a digital learning environment. Thirty-two teachers were randomly assigned to formulate scenarios either based on their personal experience or with assistance from their preferred GenAI tool. The findings reveal systematic, complementary differences. Scenarios drawn from teachers’ personal experience effectively captured socio-cultural dimensions, including home life and local cultural holidays. Conversely, GenAI excelled at helping teachers elicit internal factors and professionally grounded perspectives, such as the teacher’s inefficient management of instructional time. Notably, both methods demonstrated limitations in producing strong scenario narratives. These results suggest that human-GenAI collaboration offers immense value for teachers’ professional development by successfully bridging explicit training instruction with personal experiential knowledge and structured GenAI outputs, contributing critical insights into the emerging field of human-GenAI interaction in educational settings.