Some functions of the cyborg's brain would be locked or digitalised. It would be programmed with various functions such as absolute obedience to the people in authority and so on, before it regained its freedom. This also made it difficult for the cyborg to carry out scientific research, pilot spaceships and perform other actions which required high-level brain activity.
Simply put, if Sheyan chose to bring the three cyborgs, it would be equivalent to gaining three servants, slaves, cannon fodders, scouts, sentries, etc.... To have three such assistants in that horrible, unexplored jungle environment would definitely be of great benefit -- provided, of course, that they could land safely.
Sheyan had already grouped up with Aldaris. After all, the trust between them was much stronger than with the others there. Sheyan was still hesitating on what to bring with the remaining space, but Aldaris just casually selected the three cyborgs on the option list, then threw the pen aside.