While I make no claim to firsthand knowledge about the CF physical testing, when I was younger I completed a physical fitness test for Policing that was regulated pretty stringently.
The push-up requirement had us touch our nose to a gym mat that was approximately 2 inches off the ground. Additionally, the instructor counting had a tennis ball in his hand, with his hand under our stomach. (He was lying on the ground next to us counting.) His count increased only when our stomach touched his hand, and our nose touched the mat (must be at the same time). If just our nose or stomach touched, it didn't count. To this day, I still have nightmares of doing 50+ what I thought were quality push-ups, but only scoring 47 and hearing him yell "LOWER - THAT'S NOT A PUSH UP!".

If you're worried about proper form, put something (IE: tennis ball) under your stomach and nose.
Touch your nose and stomach at the same time and you'll know your form is correct and you're getting low enough.
At the very least, you'll be able to eliminate some "LOWER – THAT’S NOT A PUSH UP!" counts.

Best Wishes
That's exactly why I hope it's still there. I can do 27 consecutive push ups as it stands now, but if for some unknown reason (Maybe form?) something goes wrong, and I only get 17 or 18 push ups done.. It's nice to know I won't get sent home straight away.
The way I do my push ups is as follows:
-Hands shoulder length apart
-Down until my arms are at a 90 degree angle, I don't think you need to touch your nose to the ground...
Hopefully that's correct. I believe it is though.