it is nonsense: independent sharing. It's either independent or sharing.
INDEPENDENT - "Not dependent; free; not subject to control by others; not relying on others; Separate from;"
SHARED - "To partake of, use, or experience, with others; to have a portion of; to take and possess in common; as, to share a shelter with another".
Flat might be either independent - to belong to one person/family, or shared - to belong to more than one person/family.
It's like to say: I sell a new old car, or i go on long short cruise, I am a slim fat person.. I think he is just a smart stupid advertiser.

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Whatever Turns You ON...
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