The sentence in your question is self-contradictory. Only when the fluctuations are large enough can you make money, otherwise you have to lose money. So it is obviously not a "guaranteed profit but no loss".

The advantage of buying two-way equal-volume options is that you don’t have to bet on the direction. You only need to bet on the volatility. You can make money if it rises or falls enough. But the disadvantage is that when you pay, you lose more. For example, if you buy a call option and the stock price does not move when it expires, what you lose is the premium of the call option. But if you bet on both ends and the stock price does not move when the time comes, you will lose one call premium and one put premium, and the risk actually increases. Therefore, there are gains and losses. In the financial market, risks and returns are proportional.

Another problem is that the volatility that has been considered when pricing options is fully reflected in the price. This means that options with higher volatility have higher prices (because they are more likely to make money). Only if the actual realized volatility is greater than the expected volatility when the option is priced, the buyer can make money. For specific relationships, you can look at the Black-Scholes model.

There is a structured product called Twin-Win Certificate, which is similar to this strategy, but it is not actually structured as you describe because the cost of hedging is too high. Generally, the income far away from both ends is given up (that is, there is a income cap) to reduce costs.