In these items (immersion or oven), if the L to E is open circuit (as it should be), and the L to N should be, say 19Ω, then there is no way any fault in the filament could result in this resistance becoming lower, reducing to 0.3Ω.
But this (new, from ebay) element is not known to have ever worked - For all we know, L+N are directly connected inside the element and it's an absolute short with only ~ 1m flex worth of resistance, which is pretty negligible.