Hi you might want to see which of your level HOs are trigerring more UL Level or DL Level. in UL the minimum decodable level is very low compared to DL so if your thresholds for HO are properly set and with them the DL LEvel HO count is higher than UL LEvel then its logical for going to TCC.
Do a Trial on such region where sites are far off and coverage issue and the DL LEvel hos are high would show you the improvement.