Don't worry, he is a full RO and you're on the right path. Every RO has its own dynamic, and Ada/Omar's is fwb to lovers. Right now, Ada/Omar doesn't feel anything romantic for the MC, they are just physically attracted to them, and what you choose in chapter 9 determines how they'll behave towards the MC from that point on (whether they keep flirting or try to keep their distance sentimentally speaking to not hurt the MC further), but I assure you that there will come a point where those feelings will inevitably change, and Ada/Omar never shy away from expressing themselves openly. When they start to fall for the MC, they'll say so without a problem.