That's not exactly true.
In FY3/2014, Sony projected selling 15 million PS3+PS4 units, and they ended up selling 14.6 million.
If anything, I'd say that their projections have been very accurate. The biggest discrepancy throughout the PS4's lifetime was only +1.7 million, and the average is +0.64 million. In the same period, Nintendo's biggest discrepancies were -5.76 million for 3DS, -6.28 million for Wii U, and +5.05 million for Switch.
3DS and WiiU saw a lot of jokes for all the revision of forecast being severely lowered and fans defending that this new projection would be easy to hit and them they miss.
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"
Azzanation: "PS5 wouldn't sold out at launch without scalpers."