Here is an interesting viewpoint on terminology, from the 1988 document "A History of US Army Lessons learning" by Dennis J Vetock.
"One relatively minor but inescapable conclusion became increasingly apparent during the course of this study.
"“Lessons learned” is an unsatisfactory term as commonly used. In virtually every substantive and grammatical instance, “lesson” sufficed for the redundant two-word noun. For a commander to report after an action, for example, that he learned three “lessonslearned” grates upon the tutored ear but, more importantly, implies incomplete understanding of the overall process.
"That commander may have personally learned some lessons but the US Army did not.
"An army learns lessons after it incorporates the conclusions derived from experience into institutional form. Out of the commander’s experience may come a lesson, and from that lesson may come new or adapted doctrine or perhaps dissemination of potentially useful information. Only after its institutionalization can the lesson be correctly described in the past tense as a lesson learned. Until then it remains just a lesson or usable experience, a semantic distinction that few fully appreciate.
"We need to speak of “usable experiences” or “lessons” and avoid using “lessons learned,” for once an army learns a lesson, the lesson disappears into doctrine, organization tables, or training programs. Lesson learning is a process, not a product.
"“Lesson” alone accurately describes processed experience, but trying to change an everyday speech habit may be presumptuous - and not unlike emptying the sea with a bucket. Still, a new consciousness in terminology represents a step toward fuller appreciation of how an army learns lessons."