They prescreen you docs before charging fee and they also hold a very consistent basis. No “under table rules”
I think one of the reasons why TTEO is so applicant-friendly:
Most mainland Chinese applicants can’t apply in tteo unless they held a resident ID in Taiwan. So officers there are yet being bombarded by fake documents.
I also got approved the same day. Although I am a Taiwanese citizen, but I did see foreign passport with DTV on their desk.
TBH, if your docs are not qualified you will be turned down in 1st stage without charging you any. If they accept your docs, then 90%+ you will be approved.