That's not foolishness, rather a business strategy of rail board. First of all, with present TT proper maintenance wouldn't be possible for Coromondal at HWH. By sharing rake with Chennai Mail, Coromondal gets that. Also by sharing rake between these two trains entire operation becomes possible with only 6 rakes, whereas without RSA it would need total 8 rakessame applies for Gitanjali also. However, you are right that RSA is not possible (or I would say needed) in between GT and TN as both of them have very close slot.