Surplus calories aren’t necessarily required for muscle growth. Your body will use excess fat that’s already there, but I’d agree you can accelerate the process by eating more. It really is a question of how much fat you’re comfortable having in pursuit of the bulk. You are right that if you start out at like 5’9 140 lbs you’re never gonna look big (in clothes) if you stay at that weight
Let me rephrase. Building muscle requires calories. If you're bulking (putting on weight due to being in a surplus) you know you're getting maximum muscle growth. If you are eating less you might be right at maintenance, or you might be leaving gains on the table, which is why bodybuilders bulk and cut. If you're comfortable with your body during the bulk i don't think it's that big a deal to gain weight. i think the fear of looking fat keeps a lot of skinny noobs small
That's why you keep your surplus small. It's very possible; when I was bulking I gained a pound every three weeks. That's also why you cut. I can understand not wanting to bulk and cut, but there's a reason it's so common. It works, and if you want to maximize muscle gain or break through a strength plateau you should do it.