To put it briefly, the point of very small bets is to not lose the bankroll in the worst-case scenario. Let's say the effectiveness of your strategy is 60%. That is, for every 100 bets you will have 60 winning and 40 losing ones.
1. It is logical that these bets will be fixed in size.
2. At the very beginning, the size of this fixed bet will be approximately 1/1000 of the bankroll.
3. 60 winning bets should significantly exceed the size of 40 losing ones.
The thing is that average values are characterized by dispersion. And if on average you have 60 winning bets out of 100, this does not mean that within each hundred bets you will have exactly 60 winning ones. It may well be that at the very beginning the ratio will be different. And you will come to the ratio of 60/40 only with a very large number of played bets (about 1000).
Here is what the author writes about this in the book "How to beat the line of the handicap"
I agree, this sounds very reasonable.
If your strategy is 60 percent effective, then it is pretty close to 50 percent effective. With a small number of bets, the probability of losing (despite the good overall effectiveness of the strategy) is very high. This is a big risk that is worth reducing. The more times you bet, the closer your actual probability of winning will be to the desired 60 percent. In this example, 1,000 attempts will be better than 100 attempts, and 10,000 attempts will be better than 1,000 attempts (all other things being equal).
The more interesting question, in my opinion, is how to measure the effectiveness of your sports betting strategy (i.e. how to determine that your effectiveness is exactly 60 percent)? Experimentally?