Does the 20% p.a. strike one as a credible return on an investment-grade wine? Why or why not?

Turns out wine has actually not been a bad investment in recent years (in absolute terms...relative to stock market it has seriously underperformed).

However, 20% is crazy.

https://www.wineinvestment.com/wine-investment/market-performance/

The two main reasons 20% is a crazy return? 1) The asset does not generate recurring revenue (and has no potential to, unlike land or a company) 2) Scarcity only increases slowly over time

I would agree that it is not credible. 

The only reason to justify 20% would be if there is unexpected demand increase (say a certain label, varietal, vintage, or combination thereof drastically increases in popularity for some reason) or if there was some risk involved.  Neither are likely.

If everyone could predict the price rising 20% YoY, the initial purchase price would be much higher.