Don't compare one Dell model with another, that's why they're different models, all specs aren't the same. If all those E-models are reporting the same result, that suggests either it isn't supported or a bios update is required. the bios may not address the issue as Dell usually doesn't say what a bios update does. But, you should check the current bios level amongst the same Dell model. AND NO, this still not the same bios update on a different other models. It may not be a bug but the E-model doesn't support booting from a USB drive or you need to set it within the bios if applicable. An actual bug maybe involved and only Dell can address that, so check thier support forum or the Dell forum here for further help.