Right but think about the counterfactual. Those people living in that new complex didn’t just spring into existence on the day it opened. Wherever they were living before, they were creating traffic and emissions there too.

If they were living in a suburban or rural area, and now they live in a city, just going about their day-to-day lives is generating fewer emissions than they were before - cities (where people live close to each other and use more public transport) are generally much greener than suburbs and rural areas (where people drive a lot).

If they were living in an old building and now they are living in a new build, they probably now have a much more energy efficient home with much better insulation, and so now they’re contributing fewer emissions every year through heating their homes etc.