Also the codex does mention somewhere, I believe in ME 1, that sleeping pods are shared between crew members. So given 3 rotations, you don't need that many sleeping pods/bunks as at least 2/3 of the crew will be up and active at any time. Given that the Normandy was designed as a warship rotation schedules will likely be fairly detailed and specific enough to ensure the efficiency in sleeping pod usage.
As for why the SR2 has a smaller crew compliment than the SR1 despite it's bigger size, you must take in to account where the quote about permanent came from. I don't recall that statement myself, but if occurs, based on dialog choices, before awakening Grunt, then one thing is fairly obvious. The statement was said of the SR2 during it's time with Cerberus one a volunteer suicide mission. Cerberus was until two pretty stringent constraints when they were staffing the ship. Firstly, the crew members had to be willing to risk their lives in a likely suicide mission and secondly they needed to present a friendly/relatable/kind face for Cerberus. So they couldn't be crazy die hard mercenary types like Zaeed or true believes who would do anything Cerberus asked. (Despite Zaeed being part of the ground team, he was explicitly a hired merc and therefore not a representative of Cerberus and the values they wanted to try to sell to Shepard.)
So staffing was likely slim picking which is why they had to grab so many recently ex-alliance people like Joker, Chakwas, Ken, and Gabby. As well as people who were likely not Cerberus before signing up like those crew members in the crew quarters that have family in terminus colonies.
What we can infer is that 24 is more than the bare minimum needed to run the ship with a Skeleton crew. (the Normandy was, I believe, crewed with a skeleton crew from leaving Earth, until arriving at the Citadel.) But if you remember the first scene for ME1 we see Kaidan sitting next to Joker, and in the intro to ME2 we see Presley and an unnamed female crew person sitting up in the bridge. We know that Kaidan's usual station is on the crew deck near the sleeper pods and the lockers. We also know that Pressley's normal station is on the port side of the stations near the galaxy map. So either they performs multiple roles as part of their duties (very likely) and/or most stations can login into the work interface of any duty station (also very likely). Some stations may also act as secondary stations for duty stations from other parts of the ships such as the Gunnery station and engineering. Someone from those sections might have someone on the bridge during critical moments like battle to allow the Captain/Commander act in the most efficient way possible.