Actually, while I am by no means an expert on the rules of golf, I don't believe you're correct that the rules define a drop area the way you describe.
Under the local rules section, however, dropping zones are defined. It appears to me that WGT is adhering to those rules, implicitly claiming that "it is not feasible or practicable to proceed exactly in conformity" with rules governing water hazards (i.e. 26-1).
See below.
Yes, you are absolutely correct that WGT does not provide players with all the options that one would have if playing in real life. But I don't think it would be practical for them to do so. For example, I have to be believe that allowing players to go back on a line as far as they would like to drop the ball just would not work.
So, yes, I agree: they don't have it exactly correct. But I have to disagree that fixing it is a priority at all.
6. Dropping Zones
The Committee may establish dropping zones on which balls
may or must be dropped when the Committee considers that it is not feasible or
practicable to proceed exactly in conformity with Rule 24-2b or Rule 24-3
(Immovable Obstruction), Rule 25-1b or 25-1c (Abnormal Ground Conditions), 25-3
(Wrong Putting Green), Rule 26-1 (Water Hazards and Lateral Water Hazards) or
Rule 28 (Ball Unplayable).
Generally, such dropping zones should be provided as an
additional relief option to those available under the Rule itself, rather than
being mandatory.
Using the example of a dropping zone for a water hazard,
when such a dropping zone is established, the following Local Rule is
recommended:"If a ball is in or it is known or virtually certain
that a ball that has not been found is in the water hazard (specify location),
the player may:
(i) proceed under Rule 26-1;
or
(ii) as an additional option, drop a ball, under penalty of
one stroke, in the dropping zone.