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However, suppose we make a slight change to opener's hand:

In standard methods, using fourth suit forcing, the auction now begins:

What is opener to do at this point? Opener doesn't want to bid 3NT with nothing in diamonds, since responder's 3 diamond was totally artificial. If opener gives a preference to the partnership has missed its best spot of 3NT.
Using 2/1 Game Force, the auction goes:

Responder rebids a natural, forcing 2NT, and opener simply raises to 3NT with nothing further to say.
So while the use of fourth suit forcing does resolve some problems in standard bidding, it doesn't resolve all of them. 2/1 Game Force will usually make the auction more comfortable for the partnership. In addition, the bid of the fourth suit can be put to a slightly different purpose when playing 2/1 Game Force. See the discussion of fourth suit in the section on Responder's Rebid in Chapter 3