I LOVE Shea Butter as a body lotion but I would have thouht it was too rich for a facial moisturizer but I could be completely wrong.  Here is what Wikipedia says and as you can see you are correct that it has some sun protection but probably not ENOUGH to be really effective.
Shea butter is known especially for its cosmetic properties as a moisturizer and emollient. It is also a known anti-inflammatory agent.[1] Shea butter is marketed as being effective at treating the following conditions: fading scars, eczema, burns, rashes, acne, severely dry skin, blemishes, dark spots, skin discolorations, chapped lips, stretchmarks, wrinkles, and in lessening the irritation of psoriasis.[citation needed] Shea butter provides natural ultraviolet sun protection, although the level of protection is extremely variable, ranging from none at all to approximately SPF 6. Shea butter absorbs rapidly into the skin without leaving a greasy feeling. In Nigeria, it is known to be very effective in the management of sinusitis and relief of nasal congestion. This is due to its emollient properties which helps in relaxing the tension in the face skin thus easing respiration. All one needs do, if one has sinus problems or congestion, is rub a considerable amount of the butter in and around the nostrils. Scarcity of supply results in an erratic market price.