Which still begs the question, where does the 104 million+ number come from? If VGChartz is correct, baring in mind that Sony had just announced PS1 crossing 100 million units in 2005, and then discontinuation in 2006; then Sony would have sold 4 million PS1's in the 12th year of its lifespan (6 years into PS2 being on the market)?
That's not necessarily true. Discontinued just means they stopped making new ones, they still would have had old stock to sell so the rest of those sales wouldn't all have been in 2006.
However that said, it does look like you are right and it is overtracked.
100% agree with you, but sales would have decreased significantly from that point on. Could it have really added up to another 4 million units after that point is what I really mean to say.
Every single source of sales has the PS1 above the Wii though. So it's not just VGchartz you are questioning but rather every sales report and analysis in the world.
I'm pretty sure that if the Wii outsold the PS1, it would have come out by now.