Two, you can't tell if a longevity breakthrough has occurred any faster than the rate at which humans happen to live. You would need institutions with the resources to collect data on the experimental groups and conduct longitudinal studies over many decades to see if they live a lot longer than the untreated control group of natural human populations. I don't know of anyone who has proposed doing that.

That's not likely to be true. If people are aging a lot more slowly, you should be able to see the effects in ten years, maybe less. It's hard for me to imagine a method which would lead to much better markers for aging that left people with the same lifespans.