So a slightly different situation - though one that happened in last year's Six Nations (must have been Wales against Scotland or France - it was in the Millennium Stadium):
Blue kicks the ball out on the full from about half way.
It crosses the plane of touch well within the Red 22 and is caught by the winger who takes a QTI to the fullback who kicks it directly into touch.
Ignoring the silliness of taking a QTI in such a situation, should red have had the gain in ground?
It is the only decision that makes rugby sense - anything else is legalistic-semantic.
However it opens up a wider issue: all the field areas defined in Law 1 include the touchlines - except of course the 22. Is there an imaginary extension of the goal line at the back of the 22 so that if the ball rolls past that, it is dead and no QTI is permitted? Maybe the failure to mention the touchlines was intended to avoid the awkward question DocY is asking: does throwing in from touch mean the thrower has put the ball into his 22?
For me the situation ought to be that:
(1) if the ball crosses the touchline touch outside the 22, then the defending side
cannot throw in for a kick to gain ground.
(2) if the ball crosses the touchline between the 22m line and the goal line, then the defending side
can throw in for a kick to gain ground (E&OE)
It should not be beyond the wit of man (or even WR) to make that clear. At the moment we have a useless muddle.