Does anyone have any definite confirmation that the rule for illegal forward pass actually changed after 1989?
Short of a copy of the 1989 rule book for comparison to the current wording, I don't know what you would consider definitive. Lacking that old rule book, I would think the following should suffice:
1. From SI:
http://sportsillustrated.cnn.com/football/news/2001/11/08/bears_packers_rivalry/
"Parkinson ruled that Green Bay quarterback Don Majkowski's hand, moving forward at the time, had not broken the plane of the line of scrimmage before releasing a pass."
2. From the Journal Sentinal:
http://www.jsonline.com/sports/packers/57784427.html
"
Editor's note: After much debate spearheaded by Bears executives, the NFL changed the rule on passes thrown beyond the line of scrimmage. What matters is where the player's body is, not the ball, when the pass is released."
As for the announcers, they are often mistaken about the rules on their first take. The replay took about 4 minutes, and as I recall they debated the rule as we waited. It took some time before they clarified the rule.
As for the Wikipedia quote in post #24, that's not what the current rule says. That wording would be consistent with the old rule. Since that writing is attributed to 1990, one might conclude it was written before the league ratified the new rule latter that year.
This circumstance is currently covered under a note added under Rule 8, Section 1, Article 2, Item 1, Paragraph (a), which reads as follows:
"Note: It is a forward pass from beyond the line of scrimmage if the passer’s entire body and the ball are beyond the line of scrimmage when the ball is released, whether the passer is airborne or touching the ground. The penalty for a forward pass thrown from beyond the line is
enforced from the spot where the ball is released."
This is not an urban legend.