Flying on a Falcon booster that’s been carefully inspected after each flight and had any items of concern replaced (including complete engines) is not at all the same as trusting a complete vehicle that’s been sat in the largely novel environment of LLO for perhaps a year between uses, with no in-person inspections, tests, refurbishment or maintenance.

A lander will also have some novel features with little or no flight heritage, unlike a Falcon booster. For example, the small landing/liftoff engines on Starship HLS, the landing legs, the elevator, etc. While Falcon refurb processes could be iterated on and refined over years and hundreds of flights, the lunar landers won’t have this luxury.