The S-IVB also ongoing to thrust at a low degree by venting gaseous hydrogen, to maintain propellants settled in their tanks and stop gaseous cavities from forming in propellant feed lines. This venting also taken care of safe pressures as liquid hydrogen boiled off while in the gasoline tank. https://ultra-low-power-soc04578.mybjjblog.com/the-smart-trick-of-ambiq-apollo3-that-nobody-is-discussing-46744731