I have personally had a lot of issue with shoulder joint issues. I hurt my rotator cuff in the military and it hasn't been the same since. I could never continue training and was always an off again off again weight lifter because of shoulder and knee problems. A friend told me he had the same issue and started not breaking 90 degrees and it helped him immensely. I did the same thing and I haven't had an issue since. I can obviously put up more weight this way too. I don't know if my chest is getting a better workout, but it's getting a workout and I can continue to go to the gym. This is definitely better. Whether your issue is the same, who knows? But it works for me and who really cares how far you go down? Honestly, bench press may be a cornerstone of weightlifting, but as far as strength goes in any type of normal situation, it's the most worthless lift of all. When do you need to use your pecs normally for any type of work whether it be your profession or at home? More importantly, when would your strength from your chest to a few inches out be necessary? I say, if you can build your chest with less risk than that's the way you should be doing it. I go a little below 90 sometimes but I never touch my chest anymore. I've been adding mass too. So it works!