Ahh. Hammer fired pistols. Never any doubt whether or not the "hammer dropped."
The barrel locks up into the slide before you fire (most semiauto handguns). It does that to insure the cartridge case walls and base are as securely supported as possible by heat treated (strong) steel as the case alone cannot support the pressure generated with the round is fired.
If the barrel was not securely "locked up" in the slide then you would not get that very slight delay between maximum pressure and the bullet leaving the barrel (which drops the pressure very rapidly to a safe level.) The result could be (if it wasn't fully locked up when the round fired) the slide moving rearward too soon and the case rupturing and dumping 35,000 to 40,000 psi of pressure out into the frame/magazine/slide resulting in damage/destruction to the pistol and the shooter.
Oh, I guess the XD/XDM pistols have a visible striker position indicator (forgot about that) so you'd know if the striker was released on one of those, too.
One other thing - you've got a striker block in the slide. I'll bet, when the slide is part of the way back, the striker block is not lifted into position to clear the striker as it moves forward when released by the sear. Had a repeat timing issue on an M&P once. I could hear a "click" but would have no mark on the primer. The trigger bar was not fully lifting the striker block upwards. The sear would release the striker and the striker would fly forward but hit the striker block and be stopped before it could hit the primer and set the cartridge off.
Good luck with it.
One more thing (getting old = I blame it on getting old) you can try to ease your mind. Make sure the pistol is empty, empty, EMPTY! Then, with the slide forward, place a pencil in the barrel and point the muzzle up. Pull the trigger. Does the pencil bounce upwards? If so it's because the striker hit it when the sear released the striker. Now, do it again, except use one hand to push the slide back even with the frame and squeeze the trigger again. Did the pencil bounce up the same amount? If so, you may have a problem as the striker block isn't blocking the striker's forward travel speed/energy.