nginx .Net core webapp: Why should we use proxy and replace default configuration of nginx

According to the fowlloing microsoft page, in order to do the https configuration, we should use proxy and replace the default configuration of nginx.conf by the suggestion of microsoft:
Linux with Nginx

Before i did this change, everything worked actually well and as expected. After doing these steps, i’ve got a lot of 503 exceptions by calling my page in the brwoser.

I could solve this problem by changing limit_req zone=one burst=10 nodelay; to limit_req zone=one burst=100 nodelay;

But in that tutorial of Microsoft they didn’t explain why we should make this steps and my question is, would i get any trouble in the future if i would skip this step and just keep the default nginx.conf without proxy?