The Saiga is not a proper AK.
It's more "proper" than just about any other AK on the market, seeing as it's built on the same Russian assembly line at Izhmash as the modern AK-74M and AK-100 series rifles.
The Saigas share hammer-forged chrome-lined barrels and many other common parts with their respective military counterparts, and many Saigas sold commericaly on the international market are practically identical to the the military rifles, aside from lack of select-fire.
The Saiga sporter sold in the US to meet 922(r) regulations can be easily converted back to the standard pattern with a few tools, a conversion kit, and a Saturday afternoon. Your end result will be closer to a modern-manufacture stamped Russian AK than just about any rifle out there. Which is exactly why Arsenal stamped receiver rifles, among others, start life as Saigas.
Now the Saiga 308 is a slightly different beast, as its receiver (like the VEPR) is based more closely on the (AK-derived) RPK design than a typical AK.