The background of this recomendation in the HSMI manual is the working principle of MOX technology, which reacts with oxygen.
From your post it is not clear whether you would like the sensor to temporarily survive these conditions, nor whether the sensor will be operated, or if you are interested in air quality during this period.
Theoretically we don't expect your conditions (oxygen replaced with CO2) to damage the BME680, but since we have no practical experience with these conditions, you would need to test them on your own. Note that you would also need to consider which other compounds are present and in which concentrations, if any.
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