MATLAB: Matlab Bug? cell array of containers.Map

cell arraycontainers.map

I have two expressions. In my opinion, both are equal. But one works, the other causes a matlab error.
for your info: obj.TabData is a 2×1 cell array [103×1 containers.Map] [163×1 containers.Map]
expression 1)
mapObj = obj.TabData{1}
causes "Expected one output from a curly brace or dot indexing expression, but there were 3 results."
expression 2)
temp = obj.TabData;
mapObj = temp{1};
works. mapObj is Map with properties: Count: 103 KeyType: char ValueType: any afterwards.
Is this a Matlab Bug? Or can anyone explain this behavior, please?

Best Answer

"In my opinion, both are equal"
They aren't.
"Is this a Matlab Bug?"
No.
"Or can anyone explain this behavior, please?"
https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html
https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists
Your code does what I would expect if obj was not scalar. Basically you are doing this:
>> obj = struct('blah',{{1,1},{2,2},{3,3}})
obj = 
1x3 struct array with fields:
    blah
>> x = obj.blah{1} % cell indexing into comma-separated list -> error
Field reference for multiple structure elements that is followed by more reference blocks is an error. 
>> x = obj.blah % take first output of comma-separated list -> no error
x = 
    [1]    [1]
>> x{1}
ans =
     1
Read this to know why the second example works:
https://www.mathworks.com/matlabcentral/answers/344486-generate-comma-separated-list-in-single-line-of-code
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