The context here is betrothal in marriage, though one might argue it is consummating a marriage. Now a twelve-year old and an eight or nine-year old are rather different, and Mohammed consummated his marriage with A’isha so much earlier than even the barbarians.
On the Veiling of Virgins sura ya 11 uk.34. Sasa mtoto mwenye umri wa miaka kumi na mbili na wako tofauti na Muhammad aliyeikamilisha ndoa yake na A’isha kwa tendo la unyumba akiwa na umri mdogo zaidi kuliko ule wa washenzi.