I have all 4 Flutter SDK channels installed. The stable channel is on my PATH, and I swap to the others via the status bar in VSCode.
If I have a project open using the dev channel, and I use the Flutter: New Project command, the new project appears to be created using the SDK on my path (stable) instead of the active SDK (dev). To clarify: I'm running Flutter: New Project in an open project displaying the dev SDK in the status bar.
The resulting project opens with the stable SDK selected in the status bar, and does not show web as a target platform, which makes me believe it was built using the stable SDK. I have to manually use the dev SDK to run flutter create . (because it isn't available via VSCode)