The problem developing for cloud applications like NetSuite, is that you don't get a simple, throw-away environment cloned from production to just develop your small change on, test, and approve, and forget forever.
The problem doesn't reside on source control, but in having an isolated and controlled environment to develop and test on. Which is way simpler in let's say... Magento for example.
---
That being said, It's definitely possible running different code branches in NS by having multiple domains in sandbox (if they develop using themes and extensions), and SSP Applications (if they modify the core, or the version is Kilimanjaro or older, this is needed too).