This question comes up every week now. Below is a post from someone else inquiring. On my phone so the spacing is off.
UPDATE:
Leaving the full story for "future reference's" sake in case someone else has this concern down the road.
I called CZ back because I wasn't convinced by the first explanation I got. He had made it sound like the SPRING was supposed to be holding the block shut. Of course maybe the communication error was on my end. Dunno.
He explained to me that the triangular nub plays two different roles depending on the position & movement of the trigger/trigger-bar/disconnector.
For the record, here's the breakdown:
When the trigger is in the forward/active position, the trigger connector is in physical contact with the striker connector at all times, and holds it rearward, effectively playing the "firing pin block" role while the firearm is in that state. It's actually true that in this state, the block is not "secure," but it doesn't matter because the trigger connector/bar itself is doing its job.
When the trigger is being pulled, the movement of the trigger bar rearward at its "raised" level uses the SIDE of that triangular nub to disengage the safety and pull it sideways (rightward if you're looking down the length of the pistol from behind).
When the trigger reaches the rearward position, the connector drops downward (causing the striker to release) (you can see this when pulling the trigger forward and rearward when the slide is off). It's SLIGHTLY raised after firing, which allows the striker to re-engage against the trigger connector and pull it a little rearward when it cycles forward (this pressure also enables the trigger's reset when released after the slide cycles).
SO, as for the triangular nub's OTHER role: when the trigger connector/bar is in the lowered/down/rearward position and the slide moves back forward, that triangular piece is now moved down & rearward and into the proper position for the TOP of it to forcibly hold the striker safety/block in the "closed" position, leftward. So the SIDE of it disengages the safety when pulling the trigger, and the TOP of it then holds it closed in the rearward position, after the slide has cycled.
So...it's actually an elegant, if unusual design, and I was wrong to be worried. The spring on the block/safety is only really used to move it back into place to allow the triangular nub to do its job when the slide moves back forward.