As cool as this is, the "20x improved efficiency" is not what that paper says it seems:
> Over the course of the optimisation, CO2 fixation efficiency in the CETCH cycle improved by almost a factor of 20 until version 5.4 (Fig. 2).
> This is comparable to the few reported attempts to measure the CBB cycle in cell extracts (1 to 3 nmol min−1 mg−1 CBB cycle protein,
So what it actually says is: They improved CETCHs efficiency by 20x during the development, but it is not 20x more efficient than plants, but rather comparable (although it seems hard to measure what plant efficiency is)
> Over the course of the optimisation, CO2 fixation efficiency in the CETCH cycle improved by almost a factor of 20 until version 5.4 (Fig. 2).
> This is comparable to the few reported attempts to measure the CBB cycle in cell extracts (1 to 3 nmol min−1 mg−1 CBB cycle protein,
So what it actually says is: They improved CETCHs efficiency by 20x during the development, but it is not 20x more efficient than plants, but rather comparable (although it seems hard to measure what plant efficiency is)