1) Not sure what you mean with "stuffing". 2) An unofficial website doesn't count as "proof". 3) Even the website you posted mentions the 68,954 as the maximum capacity.
That number is the "real" maximum capacity as authorized by the city government. However, for league games the used capacity is a smaller number, varying each year. Last season was 48.297, which was the last number we had in the database, and recently that was updated to 58,445 in both Pumas and Liga MX official sites, which will be the number we have in the database for the next update.