Nobody is saying that. The data gets harder to interpret for older people because they're very frequently weak and about to die of something. Some part of why stats seem to vary between countries may be due to differences in recorded deaths, which can be somewhat arbitrary when there are multiple conditions. Sort of like how a lot of HIV+ people die of pneumonia but was the cause of death that or the underlying condition of HIV?

John Ionnadis has been writing about this:

https://www.statnews.com/2020/03/17/a-fiasco-in-the-making-a...

He's a medic, epidemiologist and author of "Why most published research results are wrong", probably one of the most influential papers of the last 20 years across all of science. He says:

even some so-called mild or common-cold-type coronaviruses that have been known for decades can have case fatality rates as high as 8% when they infect elderly people in nursing homes. In fact, such “mild” coronaviruses infect tens of millions of people every year, and account for 3% to 11% of those hospitalized in the U.S. with lower respiratory infections each winter. These “mild” coronaviruses may be implicated in several thousands of deaths every year worldwide, though the vast majority of them are not documented with precise testing.

The whole essay is worth a read. It has more to say about questionable use of data and analysis than SARS-CoV-2 itself but is worth reading regardless.