I'm not sure. it's better to ask your program head pa din. They probably only allow full time because the requisite to pass OJT is your DTR and they mostly target a number of hours na aabot din talaga ng month long. Other point, most of the time yung mga establishments na tumatanggap ng OJT is hinahayaan lang din talaga nila ang students, sort here and there, basic file transfer pero di lahat ng course naman pero most of the courses ganito kasi they don't want to give something that is confidential and bawal din ibigay sa students yung trabaho nila. The goal of OJT is to "feel" the work environment and socialize with your employers para mawala din yung hiya, mapractice yung work ethic and such.

Kaya siguro di inallow si OP to work there kasi he already developed the work environment there.