The company said this would be the boosters final mission “Due to the additional performance needed to launch these payloads to geosynchronous transfer orbit.”

https://spaceflightnow.com/2026/07/21/live-coverage-spacex-to-launch-novel-geosynchronous-robotic-servicing-satellite-on-decade-long-mission/

Sounds like they're using all of the booster's fuel to launch the payload higher instead of saving some so it can return and land.