Hello,
Filtering the AD_PERFORMANCE_REPORT to keyword ID 3000000 will not match the DISPLAY_KEYWORDS_PERFORMANCE_REPORT in many cases.
Rows in AD_PERFORMANCE_REPORT with keyword ID 3000000 represent Display impressions where the single attribution model decided that a Display keyword was the most relevant criteria. This will exclude rows where a different type of criteria was chosen. For example, Placement criteria, User list criteria, etc.
In contrast, the DISPLAY_KEYWORDS_PERFORMANCE_REPORT will show all Display impressions summarized by their Display keyword, even if the single attribution model did not choose the Display keyword as the most relevant criteria for a given impression.
Let me know if you have any further questions.
Cheers,