The medium-btree has some regression as per the below snapshot and first build that shown the regression has the following commits.

1. WT-7852 Don't release eviction server lock when evicting pages (#6805)
2. WT-7828 Run many-coll-test on different variant (#6783)
3. WT-7837 Clear updates structure in wt_hs_insert_updates after processing each key (#6791)
4. WT-7856 Enable flush test with open cursor in test_tiered04 (#6806)

The reason for the drop could be WT-7852.