Nxperia Transistor PCB mounting
No, there is no trick. This pin is intetnally connected to the exposed pad under the transistor - thus it don't have to be connected.
These kinds of higher power transistors have exposed pad under them (on Your image it is visible on the left) - it is internally connected to the &quot;middle&quot; pin, so transistor still has 3 connections.
Keep in mind that this pad acts also as heatsink, so it may be needed to put some thermall mass around it. (but cooling smd packages is completly different story)
Hope this helps.