BF ticket: https://jira.mongodb.org/browse/BF-24265

The introduction of WT-7872 results in a 20% performance decrease in mongo test bestbuy_agg_merge_same_db, specifically the merge_into_bestbuy.target_identical_distribution_merge_insert_1_1 stat. Reverting WT-7872 returns performance back to its original values.

Definition of Done:
Investigate the cause of this regression and determine the correction. 
After correcting target_identical_distribution_merge_insert_1_1 is back at it's pre-7872 performance.