Yep, technically momentum should be allowed for in the referees interpretation of a pass... it is when the hands propel the ball forward that it should be called. That's why sometimes a floated pass can drift forward due to momentum and not be called. Is exagerated when passer gets tackled and ceases moving, makes pass look "obviously" forward, when in fact is not.
But this interpretation is different from referee to referee, just like tackle ball situation etc...