My experience first week of December 2023. similar to several experiences earlier this year:

I arrived in business class at about 11:30pm (but have had the same experience when arriving at 11:30am). Noticed that the main immigration hall had an area labeled "business class" (I'm paraphrasing) on the right side. I kept walking, continuing to the "Fast Track Lane" between the two halls, as depicted in the photos above. Showed business class boarding pass and was told to go back to the area to the side at the main hall.

I have an LTR visa so showed that and was allowed to pass into the Fast Track Lane. I just thought it might be easier to show the boarding pass instead of taking out my visa printout. I was wrong.

I think business class arrivals and the actual "Fast Track" are separate things in 2023, and some folks may have gotten lucky to (incorrectly) get through the latter with only a business class boarding pass.