Brake Adjustable Push rod O-ring?

That's funny I just replace my Master Cylinder this past weekend, mine had Disk up Front - Drums in Rear. I removed the master cylinder with no trouble with push rod being stuck inside the rear of the master cylinder like others were saying it was going to be. Others were saying in order to re-install master cylinder I would have to remove the push rod from inside the car push into the master cylinder and put in as a pair. I put the master cylinder onto the four bolts pushed a little reached around to the back of the master cylinder with my finger and helped lifted the push rod up to center it into the rear and it went right in place, I was questioning the fact that it didn't snap in myself. I am sure it will be ok. Bleed all the brakes and all seem to be ok. Here is a video I found questioning the same issue.

Master Cylinders