No, but you do have to overload your muscles sufficiently to induce hypertrophy. Four sets of 12 not to failure for a primary chest exercise sounds more like a cluster of warm up sets rather than a real workout.
If your training above 8 reps, I don’t see why you’d have to restrict failure altogether. Its one thing to push out 4-5 solid reps on heavy bench press and if you know you can’t complete another rep to stop the set.
Its another thing to take a light weight, throw up 12 reps with some difficulty, then at your 85% mark to failure (you could of probably completed 1 more rep on your own, 2-3 more with a spotter), you just easily rack the weight.
So you are saying that it’s OK, to stop one rep short of a 4-5 rep set, but it’s not OK to stop one rep short of a 12 rep set?
I disagree. 1 rep off 12 is less volume ‘lost’ than 1 rep from 5.
So stopping one rep short on a 12 rep set is closer to your intended target workout.
4 sets of 12 might sound like a woarmup to you but not all of us train heavy all the time, especially on an exercise like the guillotine press which can strain the shoulders more than a DB bench press.
Besides, the OP professes to be too nervous of harming himself under the bar to go to failure. He would surely be more confident using the lighter weight (which with sufficient reps can of course stimulate the muscle enough to grow) than the heavier one.
Ya, I get what you are saying. I should rephrase my opinion to being that personally, for me, doing 4 x 12 not to failure wouldn’t do much. With high reps such as that, not to go failure or near failure would mean doing 6+ sets in order to get as effective results as if say I did 4x10 to failure.