It depends how you look at it, there are biologically immortal organisms. Aging can hypothetically be stopped, obviously we're not there yet. https://edition.cnn.com/2023/01/12/health/reversing-aging-scn-wellness/index.html for example.
Discussion
I think we will have to come to some common understanding of aging before I can understand the point you are making. The article you tagged suggests that two mice having a common beginning in time are somehow different in age. That doesn’t process with me and how I understand age. That one mouse may have been affected by deterioration and disease to a higher measure than the other makes sense to me. But it would not seem to have affect the age of the mice as I understand aging. To my mind, the affect of deterioration and disease is the issue, not aging.
You're overthinking it. It's just a hypothetical question based loosely on the premise that we may be able to stop aging in future.