Nope, it encourages merging in your own playground, incrementally. You can (and arguably should) still merge mainline into your branch with some regularity, say once a day.

With the issue you're talking about, that's why we have staging environments. If you're going to release A and then B, you should be staging A, and then staging A+B. It's true that if they had ZERO idea on what the other were doing, they could step on each other's toes. But it will get caught before release. And hopefully there's enough communication to at least have a vague idea of who's working on the same parts of the code as you. If you're designing things that span large parts of the codebase without consulting or warning teammates, you have bigger problems.

Without distinct feature branches, you end up in abysmal horror situations where you push something, realize you have a bug in production, but can't roll it back without rolling N other features back. Then you start hacking in code to turn the feature off temporarily, etc, which rapidly turns into a mess.