After starting the containers, if I attach to wikibasedocker_wdqs-frontend_1 container, I see log that shows that /style.less is constantly loaded:
72.18.0.1 - - [11/Apr/2018:04:50:22 +0000] "GET /style.less HTTP/1.1" 200 9443 "http://localhost:8282/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3282.94 Safari/537.36 OPR/44.0.2168.124" "-" 172.18.0.1 - - [11/Apr/2018:04:50:24 +0000] "GET /style.less HTTP/1.1" 200 9443 "http://localhost:8282/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3282.94 Safari/537.36 OPR/44.0.2168.124" "-" 172.18.0.1 - - [11/Apr/2018:04:50:25 +0000] "GET /style.less HTTP/1.1" 200 9443 "http://localhost:8282/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3282.94 Safari/537.36 OPR/44.0.2168.124" "-" 172.18.0.1 - - [11/Apr/2018:04:50:27 +0000] "GET /style.less HTTP/1.1" 200 9443 "http://localhost:8282/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3282.94 Safari/537.36 OPR/44.0.2168.124" "-" 172.18.0.1 - - [11/Apr/2018:04:50:28 +0000] "GET /style.less HTTP/1.1" 200 9443 "http://localhost:8282/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3282.94 Safari/537.36 OPR/44.0.2168.124" "-"
Looks like some kind of bug.