Hi Li,
You are correct, only the block-level (and only if they are direct children of the header - if the paragraph-level content control is inside a table cell in a table it will be preserved) content controls get stripped.
The good news is that the fix is already provided and if our QAs approve it, it will be available with one of our next LIBs.
Thank for you correcting me.
Regards,
Vladislav
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