[Gameplay] Singed with poison trail is not considered isolated??

So recently I was playing in a ranked solo/duo as . Playing as the jungler and ganking lanes I found something really odd. Enemy top laner is . When a target is isolated there will be a mark or like something identifying it. While singed was proxying the wave between the inner and outer turrets with his poison trail the mark was not there at all, even when no other enemy unit was within his area. As I progressed through the game I noticed this again around level 7 when I evolved Q. Evolved Q reduces its cooldown on an isolated target. So when I went top again to gank and Q'd singed while he had no minions or towers and only his poison trail, singed did not count as isolated and q did not reduce it cooldown. However when i ganked him and he did not have his poison trail, he had the isolation mark on him. Please look into singed and his poison trail not counting as being isolated.