It's also not true technically. Safe is relative. People died and people fainted all the time...they were just far enough away that you didn't really hear about it.
I am in my 40s and the distances that I would ride my bike as a 10 year old are shocking when I consider my own 10 year old riding them. This is because I have more stories loaded into my subconscious about how dangerous it is. Has it always been dangerous? Has it always been safe?
The fact that there exist places on the planet where going outside in the summer risks fainting or death due to extreme heat doesn't mean we should just shrug off how terrible that will be if it happens everywhere. IMO this story is a poignant way to get people to think about what we stand to lose in the too-near future.
A rough rule of thumb is that for every degree global temperatures increase temperatures on land will go up twice that amount. So with 3.5°C, which is on the low end of what we're headed for, imagine if peak summer temperatures were 13°F higher than they are now.
It entirely depends on how much CO2 and methane we emit, but these sorts of predictions are by convention pegged to 2100. Most of the emissions pathways, unless we stabilize things soon, keep getting hotter until at least 2200.
A short, beautiful, heartbreaking sample of the smaller stakes that we're gambling.