In what way is it worse? The range of values they can contain is well-specified.
And you have a frame with an operands stack where you should be able to store at least a 32-bit value. `double` would just fill 2 adjacent slots.
And references are just pointers (possibly not using the whole of the value as an address, but as flags for e.g. the GC) pointing to objects, whose internal structure is implementation detail, but usually having a header and the fields (that can again be reference types).
Pretty standard stuff, heap allocating stuff is pretty common in C as well.
And unlike C, it will run the exact same way on every platform.