Where does it say that? I'm not sure how you could read the article and conclude the EOS R is not well sealed.According to these tests, Z7 is very well weather-sealed, but EOS R is not.
Overall, the EOS R seems quite well-sealed against the weather. It passed our standard 35-minute "heavy rain" test with flying colors, and even maintained full functionality of its touch-screen and the eye-detection sensor for its electronic viewfinder throughout. Beyond that, it stood up to 50 minutes of the same soaking the day after, impressive given that its gaskets would already have been pretty wet from the first day's test. And even after this extreme soaking, it returned to full functioning after just overnight drying.