The reason CLV works as a performance metric is that the closing line is the most efficient price. By game time, the line has absorbed all available information: injuries, weather, sharp money, public money, lineup changes, and late-breaking news. The closing line is not perfect, but it is the best estimate the market produces. If your number is better than the market's best estimate, you have an edge.
The common mistake is treating CLV as a guarantee of profit. It is not. CLV is a long-term indicator, not a short-term one. You can beat the closing line on every bet for a month and still lose money due to variance. Conversely, you can lose the closing line on every bet for a month and still profit. CLV is meaningful over hundreds of bets, not dozens.
There are situations where CLV is misleading. In thin markets, the closing line may be set by a single sharp bettor and does not represent true market consensus. In props that close hours before kickoff and never reopen, your line was never compared to a closing price. In futures, the closing line is months away and the market may shift dramatically between your bet and resolution.
The practical approach is to track CLV alongside your results. If you are beating the closing line but losing money, variance is likely the explanation and your process is sound. If you are losing the closing line but making money, you are likely riding short-term luck and your long-term results will regress. The combination of positive CLV and positive results is the strongest evidence of a genuine edge.