Is "auto t=T();" not the same as "T t;"?

[Andrey Zherikov via Digitalmars-d-learn]

I have the following types (simplified version of my code):
```d
struct A
{
    int[] i;
}
struct B
{
    A[] a = [A.init];
}
```
This code:
```d
    auto b1 = B.init;
    b1.a[0].i ~= 1;
    b1.a ~= A.init;
    b1.a[0].i ~= 11;
    b1.a[1].i ~= 12;
    b1.writeln;

    auto b2 = B();
    b2.writeln;
```
prints this as expected:
```
B([A([1, 11]), A([12])])
B([A([])])
```

But this code:
```d
    B b1;      // auto b1 = B.init;
    b1.a[0].i ~= 1;
    b1.a ~= A.init;
    b1.a[0].i ~= 11;
    b1.a[1].i ~= 12;
    b1.writeln;

    B b2;     // auto b2 = B();
    b2.writeln;
```
prints this which is not expected:
```
B([A([1, 11]), A([12])])
B([A([1])])
```

Does the second piece of code shows a bug or my expectation is 
not correct (and why if so)?