You would be correct. The guy who bought this player has no other 50 year olds, and doesn't need a filler guy anyway. he has 4 or 5 players who haven't played in months already.
The main reason someone buys an old guy is to have a roster filler that is cheaper than 1000$, which is the price one normally pays to get a filler player for a scrim then dump him before his salary is paid. So yeah, one might buy a player with no skills but under 1000$ salary for that reason, but to pay 500k defeats the purpose. It is also a bit naïve to think that because the buyer isn't American (I.E. multiple account) then collusion is not possible. I'm not saying someone colluded, but I am saying this is fishy, and regardless of why it happened, 1 team got a huge break and 15 teams got screwed over.
Back in the day when there were 4 times the managers there are now this would have been addressed and fast. Those days are long gone.