This more carefully worded Nature article [1] explains that the experiment did not meet the technical definition of ignition. That is why they wrote 'ignition'

This more carefully worded Nature article [1] explains that the experiment did not meet the technical definition of ignition. That is why they wrote 'ignition' in quotes in the article title. [1] https://www.nature.com/articles/d41586-021-02338-4 https://www.nature.com/articles/d41586-021-02338-4