Snapcraft environment variable not respected with multipass vms

I’m building something that requires the snapcraft that is currently in candidate. If I freshly install snapcraft from candidate and then build my app, it works fine. However, after some hours, the feature in that snapcraft is not found anymore. I thought that this would force multipass to use the snapcraft listed in the candidate channel but having this env var there seems to do nothing:


Am I using it wrong or misinterpreting the functionality of SNAPCRAFT_BUILD_ENVIRONMENT_CHANNEL_SNAPCRAFT ?