Earlier the old Kakinada Port used to have just one platform and it was completely utilized. Hence, trains that were introduced later had originated from Kakinada Town. The new COA station which was directly connected to COA C&W (unlike the old COA station which needs rake reversal for trains to put them on pit line) was not opened at the time of introduction of 2775 because of protocol issue although station was completely ready by then. By the time of 7221's introduction, COA new station which very much can handle 24 coaches was completely operational. This was the reason why 7206,7204, 7210 and 2775 were introduced at Kakinada Town, and originate from Kakinada Town. Hope this helps.