OK, I/wikipedia is wrong!
The definition has been updated

http://www.fsis.usda.gov/wps/wcm/connect/fsis-content/fsis-q...

https://www.law.cornell.edu/cfr/text/9/381.170

Current class definitions state that a bird labeled as a Rock
Cornish-type chicken must be ``the progeny of a cross between a
purebred Cornish and a purebred Rock chicken'' (9 CFR
381.170(a)(1)(ii)), or ``a Cornish chicken or the progeny of a Cornish
chicken crossed with another breed of chicken'' (9 CFR
381.170(a)(1)(i)). While this statement was appropriate when these
chickens were originally developed over 40 years ago, today it is
doubtful that any purebred Cornish or Rock lines exist in commercial
chicken production. The names ``Rock Cornish game hen'' and ``Cornish
game hen'' are now used to identify a very young, very small, whole
chicken that is marketed as an individual serving. Although the names
refer to hens, either sex can be used since birds of this class are
sexually immature. The names ``Rock Cornish fryer,'' ``Rock Cornish
roaster,'' and ``Rock Cornish hen'' are no longer meaningful because
these birds cannot be reliably distinguished on the basis of progeny
from other existing classes. Therefore, the Agency is proposing to
define the Rock Cornish game hen or Cornish game hen class only in
terms of age and weight and to delete the class of Rock Cornish fryer,
roaster, and hen.

Also of interest

http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/2007-0048F.htm

Cornish Game Hens
Comment: One comment from a trade association stated that the term
``hen'' as used in the ``Rock Cornish game hen'' or ``Cornish game
hen'' class may be misleading because the term hen implies that these
birds are female while the definition states that the birds may be of
either sex. The comment suggested that FSIS change the name of this
poultry class to ``Rock Cornish game bird'' or ``Cornish game bird.''
Another comment from a poultry producer said that the proposed
``Cornish hen'' definition is inaccurate because it allows industry to
call a bird that is not necessarily Cornish, and not necessarily a hen,
a ``Cornish hen.'' The comment suggested that FSIS add a definition for
``poussin'' to describe the next youngest bird than the ``Cornish hen''
if the Agency decides to keep the term Cornish hen. The comment
suggested that USDA review the literature produced by the North
American Meat Processors Association (NAMP) as it applies to usage of
the term ``poussin.'' According to the commenter, because USDA is
attempting to have its regulations reflect usage in the poultry
industry, it must consider not just the production level, but also the
market.
Response: FSIS disagrees that the terms ``Rock Cornish game hen''
or ``Cornish game hen'' are misleading to consumers and that the Agency
should change the name of the class to ``Rock Cornish game bird'' or
``Cornish game bird.'' The existing terms for this poultry class, which
provides for the use of the term ``hen'' for young immature chickens of
either sex, has been in place since FSIS established this poultry class
definition. The term ``hen'' can be used for immature chickens of
either sex because birds of this class are sexually immature. FSIS is
not aware of any data to support that consumers are misled with the
reference to ``hen'' in these terms. Changing the name of the class is
likely to spur confusion.
FSIS also disagrees that the proposed ``Cornish hen'' definition is
inaccurate because it allows industry to call a bird that is not
necessarily Cornish, and not necessarily a hen, a ``Cornish hen.'' The
existing standards in FSIS' regulations do specify that a Cornish
chicken be the progeny of a Cornish chicken crossed with another breed
of chicken. However, FSIS continues to believe that it is doubtful that
any purebred Cornish lines currently exist in commercial chicken
production today and, therefore, the birds cannot be reliably
distinguished on the basis of progeny.
FSIS also disagrees that it should add a new poultry class that
would define poussin. The poultry classes in 9 CFR 381.170 represent
poultry that are typically marketed to consumers and are more broadly
used than the standards for poussin in NAMP's Poultry Buyers Guide.