Yes. Most of us who use the pumps can testify to the gains. However, what you indicated may not be a benefical approach if you are pumping below the safety limit. Let's break things down.
Safety limit is below -5inHg, or around -126mmHg. Our body internal pressure when fully erected, hard and roaring to penetrate without any ED condition is around positive 4inHg, at max, around 4.5inHg. Some achieved to 5inHg. So, safety limit is around -5inHg and less. As you read other posts, we don't use the "-" sign for brevity purposes, so don't mind that.
Now, the problem with staying at the lower limit all the time, you will get some gains, but the gains are so miniscue that it doesn't seem like you're gaining at all. The gains are in micrometers, and not milimeters. As you constantly pump 3 to 5 days a week, you'll gain little by little. However, what you will notice is the higher gains on erection quality (EQ) overall. You will not get the larger girth that you want immediately, but you will see a quality erection as you progress.
Now, gains wise, what you're gaining is girth and not length. When pumping, most of the gains diverted to girth. The larger the
cylinder of the pump, the more girth-focus gain you are endeavoring. If you're looking for length, the
cylinder must be tight around the penis to force the penis to stretch under pressure. But, to get length, you must go above the -5inHg.