There's one key difference between null as it applies to languages like C and Java versus Option<T>-like renditions of null: null doesn't infect the type-system in the latter.

Type systems can be viewed as a lattice, usually as a bounded lattice. If you look at Java's reference type system (ignore primitive types), there is a top type, aka Object. There is also a bottom type. It doesn't have a name you can spell, but it does have a single value--null. This means that null can satisfy any type, even if the type is impossible to satisfy--and as a result, there is an unsoundness in Java's type system.