Expansion of the screed opening. Different screed material?

Hello everyone,

in our new building, the screed recess for our chimney kit was initially made too small. After a complaint, it was enlarged as shown in the pictures. To me personally, as a layman, it looks quite "botched," but I could be mistaken, which is why I would like to know your opinion on this.

What is noticeable is that the enlargement of the recess was obviously done with a different screed material, possibly concrete screed, instead of calcium sulfate screed.

Is this a "normal" and "safe" procedure? Can we place our chimney safely on the installed enlargement of the recess without the enlargement "breaking off"? What should we pay attention to, do we need to complain again here?

Thank you very much for your assessment.

Best regards,
Seol

I believe that the post would be better placed in " ", which is why I would like to move the post there, see:

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