I am assuming it is a Microsoft way of giving you an option and preferences as each customers requirements is different and some prefer to use custom/Public Certificates instead of self signed Certificates. I will not go deep into the nitty gritty of Security aspects as with on field experience I have noticed many prefer custom public Certificates instead of self signed ones. However if you feel it is not correct and should be addressed I will suggest you to raise a feedback over here.
Hope this helps.
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