Yea I mean people are seeing those guys coming up now being 20, 21 years old (Pogacar, Evenepol, Bernal,...) and they are amazing already and you might expect close to 15 years of dominance from them. Just because your average pro cyclist can be very good into his mid-thirties. Time might prove me wrong, but I think for those early bloomers different rules could apply.
Like you are saying, the years between first and last GT podium might be very similar for them compared to guys with a later peak.
If e.g. Pogacar would be 27 now, having a breakout year similar to what he having right now with a first GT podium while not achieving much before, I wouldn't necessarily expect a very different career arch than I do now that he is actually just 20.
If your peak starts with 27 you could very well be great for the next 8 years, about what I predict a Pogacar could do in reality, having his peak from 20 to 28 and then starting to decline.
Of course, there will be always outliers and he might be one, we don't have a big sample size yet.