I read that CGFNS is now authorized to issue visa certification for Occupational Therapists

I read that CGFNS is now authorized to issue visa certification for Occupational Therapists and Physical Therapists. Does this mean that NBCOT is no longer allowed to do this for OTs?

No. NBCOT is still authorized to issue certification for Occupational Therapists. CGFNS has been authorized to issue the certification in addition to NBCOT. You can go through one or the other.