The definition of "meritocracy" that the article provides isn't the dictionary definition of the word; it's the first sentence of the Wikipedia article on the topic where the opening paragraphs are talking about the historical origination of the concept. The dictionary definition reads, "government or the holding of power by people selected on the basis of their ability". The Wikipedia article lists intelligence, credentials, and education as examples of potential measures of merit but the particular measures of merit used in a given meritocracy aren't inherent to the words definition.

Whether or not advancement in a meritocracy is correlated to privilege is a function of what measures of merit are used not some innate property of meritocracies in general. In the context of an open source project one would hope it is a meritocracy of ideas where the merits being judged are something like the quality of the algorithms and code.

Selena's wish to be more open to contributors that have less time to contribute isn't a question of meritocracy it is one of organizational culture; unless the merit on which they are judging people is the amount of raw time they spend on the project vs. the quality of their contributed work.