It doesn't work because you are making some matches "more valuable" than others and you are giving points to losers that no other regular match is allocated.
It's not about the winners being equal, it's about introducing a variable number of points for losers into the table system.
For example, imagine an unusual but not impossible situation where Tigers lose 6 matches in golden point in one 24-round season.
They finish with 12 wins, 6 regular losses and 6 GP losses, total 30 points. If you add 2 byes to allow comparison to previous seasons, that's 34 total points which puts you, in the last 10 seasons (some of these places are shared): 1st, 5th, 4th, 4th, 3rd, 5th, 5th, 5th, 4th, 2nd.
That's a 50% win rate and the team typically ends up in the middle of the Top 8\.
Then you have an opponent who wins 14, loses 10 regular games (plus two byes) and they finish behind you on 32 points. How is that reasonable? Or they win 15 matches, 3 more than you, but are behind you on differential
But then take that to the extreme, imagine a side that loses all 24 matches in golden point and they finish the season with 28 points (including 2 byes), which is still often enough points to make the Top 8\. How can you have a side finishing in the finals without winning a single match?
Or alternatively, imagine two sides - one that wins 12 matches and loses the other 12 in GP (no byes), total 36 premiership points. Then another side that wins 17 matches and loses 7 in regular time (34 points) - and they finish behind a side that has 5 less wins than they do.
You can't have a moving boundary for how many total points a season (or a round) might contain. It skews the table results because all matches are not equal. And in a competition of a modest number of rounds, this is emphasised because so many teams finish near each other on total points.
If your system of 2-1 was added to last week (i.e. Round 4), that Round would have been worth 19 total points (3 GP matches) compared with the normal 16 points - you cannot have this.
Imagine missing the finals because you were pipped by a team that had more losses than you, but they were GP losses.
And as briefly mentioned before, there's also the potential collusion issue, where clubs might "let" a team take the match to GP so that they aren't necessarily losing the game, but can influence other outcomes by allowing extra time.
Lastly there's the impact on the actual football - do teams suddenly become conservative if it's all locked at 75 minutes? E.g. they might stop shooting for late FGs inside 80 mins and instead kick chase or die with the footy on 5th, because dead missed FG are now worth 7 tackles and perhaps you prefer to take the 1 point definitely than risk losing all 2?