It's specifically for "jobs in sectors like agriculture and construction", not sure better buildings will help the workers out on fields and construction sites much.

Although one temperature threshold probably don't make much sense, a strict 30C across the entire continent would mean massively different things in different countries, in many countries that mean basically the entire summer off, every year.

It matters when the heat stress continues when you're not at work. You can tolerate a lot more if your body gets actual breaks from the heat.