Agreed! SAA at least give the same priority to *G as they do their own golds. *G uses the same lounge as SAA members do too.
Try fly as a *G (as SAA plat) through Frankfurt or Munich, and use the lounges. Lounges are from the 1970's, overcrowded, and dingy. The food (think cheap snack) traveled along with Charles Lindbergh on his maiden trans Atlantic flight.
Whereas Lufthansa Hons sit in a wonderful lounge all to themselves. Dining rooms, plenty of space....
Also try phone for an award seat with LH and redeem miles, no problem! Try use star miles then there are no seats. Singapore never heard of one person ever getting a F seat on A380 (been trying for years).
With SAA X and I class are the same for both * network and their own voyager members.