The tooltip is not clear. I always ignored it because I always start the industry conversion on the same turn, but yesterday I actually read the tooltip an found it unclear.

The tooltip says ''starts after first turn". Anyway if add something in the queue the effect starts on the same turn. You can check those screenshot from turn 116.

  Here I add public 3d printing on queue and the industry doesn't drop at it shoulb be, but....

... you add something else on the queue.....

.... switch place with infinite tech and the conversion happen in the same turn you put it in the queue...