I suspect that the Dashboard stats aren’t capturing accepted lines in some contexts. If you look at my history, I started heavily using the background agents at about the time that the suggested and accepted diverged. I typically start a Background Agent, Import to local chat when its complete, and then review and commit from there. I think this must break the link between the Accept/Reject and the changes that have been made, because I accepted almost all the work that the Background Agents performed and this would indicate that I accepted less than normal despite a 3X increase in suggested changes.
It could also be that lines are not “Accepted” if you close the chat without clicking the ‘Accept Changes’ button. I often just close the chat if I’m happy with the changes and it appears to make no difference.