Well that's confusing as hell if you don't know your vehicles. Never heard of such a thing. Wouldn't the vehicle still carry the year of manufacture on it's VIN/ID tag though? That's doe at the factory and registration wouldn't change that.
On a slightly related tangent, I found out that split years are common in the US on RVs. I bought a former rental unit from El Monte RV, and the chassis was a 2002 model (with an "incomplete" VIN from Ford) and the "completed" VIN (from Thor Industries) was for a 2003 model. In California, it was registered as a 2003 model, but when I moved to NV or AZ (I forget which one it was), it was registered as a 2002 model.
And speaking of RVs, bikes, and other power sports vehicles, inventory is at an all time low for a number of reasons, starting with the pandemic shutdowns of factories at the same time that demand spiked as a means of socially distanced recreation. You also have a large population of people working from home (for those that were able to keep their jobs) whose commuting expenses went to zero, freeing up cash for more discretionary spending.
Then there is the housing market, which is seeing all kinds of volatility and inventory shortages...there will be an interesting economic correction coming once more things open up and try to get back to a more "normal" way of living...