If they can't articulate a strategy that you can understand then you run the risk that:
A) It's a scam. Their strategy actually relies on dupes doing what they say while they do something different to profit off of the loss of their dupes.
B) It's luck. With many people investing, and the market generally moving up, some of them will have good returns over time even without a good strategy. The problem here is you can do exactly what they say and it may not work.
C) It's defunct. Maybe they had some plan that worked really well 20 years ago and the efficacy of the strategy has been declining. Or, as whoever it is reveals their strategy to you others see, understand, and compensate for the strategy and it stops working because of that.
If you can understand the strategy then you can account for these risks and/or determine that they do not apply.
