Isolated power supply made by two step-down transformers

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When it is necessary to use the commercial power for electronic experiments, it is best to use a 1:1 power frequency transformer as an isolated power supply, so that no matter which wire the human body touches alone, there is no danger of electric shock. Because of the role of the 1:1 transformer, the power supply is isolated from the mains, and there is no current loop in the earth. Only touching a wire will not cause electric shock unless it touches two power cables at the same time.
Then in the hands of electronic enthusiasts, there may not be a 1:1 power frequency transformer to do isolated power supply? There is a way! Ordinary step-down transformers definitely have it? For example, primary 220V, secondary 12V, with two such transformers, connect their secondary 12V terminals, the primary of one transformer is connected to the mains, and the primary output of the other is the isolated power supply. As shown below:

The first transformer first reduces the mains to 12V, and the second transformer boosts 12V to 220V. The two transformers must have the same step-down ratio to output the same voltage as the mains. Transformer power is also best, and their power determines the power of the output power. If the power of the two transformers is not the same, the power is output at a low power.