Would you say that anesthesia doesn't "directly" extend life? After all, it only makes it possible to do certain surgeries, and it's really the surgery that is "directly" extending the life. And yet "the hospital" extends lives through it's interventions, one of which is anesthesia and without which the hospital would not function or be able to do surgeries effectively.
This is just the standard problem of assigning credit when multiple causes are involved. I'd propose the same sorts of tests we use in other cases, such as considering whether in the absence of preservation it would still be possible to save someone's life with future technology. The conclusion I draw is that preservation technology saves lives in a similar way to how anesthesia extends lives by enabling better surgeries. So it's perfectly sensible to talk about preservation directly saving lives even though it's not the only technology required to do so -- after all, if the life does get saved eventually, then preservation would deserve a hefty amount of the credit. Just as anestheologists deserve a hefty amount of credit whenever a surgery is performed successfully, and anesthesologists can be said to be directly extending people's lives directly through their work, as a critical pillar of a surgical team.
Dealing with x-risks in a satisfactory way and inventing uploading technology are also necessary to save someone's life, and will deserve substantial credit if lives are truly saved. And preservation is a substantial and irreplacable part of the constellation of truly life saving technologies for people alive today.