have you tried calling it like this
[bool_val, byte_array] = obj.GetLatestBuffer();
This works fine for me in 14a with the following example
public bool GetLatestBuffer(out byte Buffer)
Buffer = new byte;
for (int i = 0; i < 10;i++)
Buffer[i] = (byte)i;
>> a = ClassLibrary1.Class1
Class1 with no properties.
>> [bool,array] = a.GetLatestBuffer()
Byte with properties:
SyncRoot: [1x1 System.Byte]
SideNote: The out keyword forces the routine GetLatestBuffer to assign Buffer to some value. So you do NOT need to pass down a preallocated array and since you dont need to do this it appears as output in MATLAB directly.
Also in C# when using OUT you never pass down a preallocated array. So what MATLAB does is correct here and matches the .NET programming.