This paragraph does not establish a containing block for any of its descendant elements that are absolutely positioned. Therefore, the absolutely positioned boldface element it contains will be positioned with respect to the initial containing block.

Thanks to position: relative, this paragraph establishes a containing block for any of its descendant elements that are absolutely positioned. Since there is such an element-- that is to say, a boldfaced element that is absolutely positioned, placed with respect to its containing block (the paragraph), it will appear within the element box generated by the paragraph.