Логи там такие:
x86_64; rv:76.0) Gecko/20100101 Firefox/76.0"
127.0.0.1 - - [13/May/2020:21:34:33 +0300] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:76.0) Gecko/20100101 Firefox/76.0"
127.0.0.1 - - [13/May/2020:21:34:33 +0300] "GET /static/js.js HTTP/1.1" 304 0 "http://localhost/" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:76.0) Gecko/20100101 Firefox/76.0"
127.0.0.1 - - [13/May/2020:21:34:33 +0300] "GET /static/css.css HTTP/1.1" 304 0 "http://localhost/" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:76.0) Gecko/20100101 Firefox/76.0"
127.0.0.1 - - [13/May/2020:21:34:33 +0300] "GET /static/img.jpg HTTP/1.1" 304 0 "http://localhost/" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:76.0) Gecko/20100101 Firefox/76.0"
::1 - - [13/May/2020:21:34:44 +0300] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36"
::1 - - [13/May/2020:21:34:54 +0300] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36"
Т.е. и Мозила шлет 4 запроса, а Хром шлет один - на html.