Jihad wasn't lying; he truly had no particular thoughts about keeping Gao Yang behind. Although he didn't believe Gao Yang's claims at all, Jihad still didn't report the presence of Gao Yang and his group to his superiors.
In fact, even if Jihad had reported the situation, it wouldn't have made much of a difference. Syria was such a chaotic mess that no one cared about their origins, especially since Gao Yang and his men had helped the government forces to achieve an unexpected, outstanding victory that nobody from top to bottom had anticipated.
The situation in Syria was already a complete shambles, with the government forces in constant retreat and both the Defense Minister and Deputy Defense Minister killed in bombings. Everyone was simply too relieved by this major victory to care about the specific details of Gao Yang and his group's involvement.