Why nginx selects server block with _ server_name? - nginx

Question

My simple nginx.conf:
http {
sendfile on;
tcp_nopush on;
types_hash_max_size 2048;
server_tokens on;
include /etc/nginx/mime.types;
default_type application/octet-stream;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3; # Dropping SSLv3, ref: POODLE
ssl_prefer_server_ciphers on;
access_log /_nginx_logs/access.log;
error_log /_nginx_logs/error.log;
gzip on;
server {
server_name www.example.pro;
listen 80;
listen 443 ssl;
return 301 https://example.pro$request_uri;
ssl_certificate "/etc/letsencrypt/live/www.example.pro/fullchain.pem";
ssl_certificate_key "/etc/letsencrypt/live/www.example.pro/privkey.pem";
}
server {
server_name example.pro
listen 80;
listen 443 ssl;
ssl_certificate "/etc/letsencrypt/live/example.pro/fullchain.pem";
ssl_certificate_key "/etc/letsencrypt/live/example.pro/privkey.pem";
location / {
proxy_pass http://localhost:3000;
}
location /api {
proxy_pass http://localhost:7500;
proxy_set_header X-Forwarded-For $remote_addr;
}
}
server {
server_name _;
listen 80 default_server;
location / {
root /projects/site-stub;
}
}
}
When I open my site as https://example.pro everything is ok.
When I open my site as http://example.pro, nginx answers from server block with server_name _.
Why? IP and port are the same, server_name value has exact word for Host header, but server_name example.pro not works for http://.
But it works good for https://!