I think this is the one you're talking about
Kusanku (also in pinan yondan): beginning from a natural stance with one arm in chamber and the other across the body with fist stacked on top of the chamber, perform a straight forearm/hammer fist strike at the same time a front snap kick, followed by a shuffle forward and elbow strike with the chambered arm.
The beginning position can represent an arm grab, yanking the wrist and pressing their elbow with yours, or at least opening their guard up with a pull. Then forearm towards the neck or fist to the face, the purpose not so much to do a lot of damage but to at least to distract them from the kick, which takes the knee or thigh to collapse their stance, or groin/abdomen to double them over at least, followed by grabbing the back of the head and shooting in with the elbow smash.
There is a similar forearm strike/kick in chinto, instead followed by a takedown/dropping to one knee. In this case, the target of the kick is even more important, you're definately taking the knee/inside of the leg to collapse them.
A slightly different one is also in Kusanku (as well as pinan shodan), the "chest block" and same side front snap kick. I use ot pretty much the same way, as a distraction to deliver the kick and get in close for a throw (it is followed in kusanku and pinan by a 180 turn and shuto uke in nekoashidachi, which could worked into a hip bump). Of course, it could also be simultaneous attack and defense, deflecting a punch and kicking. That's the "simple" explanation.
I find these also in the two praying mantis forms I know, with an inside snap kick and finger strike to towards the eyes simultaneously. Try it in sparring, it works all the time *lol*. You'll almost always get that kick in when they are distracted by the strike toward the face
The overall concept is masking your true attack with a feint. Sometimes you mix up the timing, maybe shooting the hand out just a little before you start the kick, or vice versa, depending on which one you want to land and how you're going to follow up. Of course, it's a bonus if both attacks land, if you've got them in a position where they can't defend at all.