WORKAROUND:
We will see from the support if this is a bug or an extremely poorly documented intended change. In any case there IS a workaround. With those templates mentioned above if you add a via, change its size and then press SHIFT+V while routing to select via size, any via size present in your design will be available from the list. So just edit the first via of a given size manually and then use it as template. Logical, but should be documented :/ Lost 3 hours to this problem.