If the page is freshly reloaded, the lock_page_icon is not shown on any changes on the page. However, if you come to the same page without fresh load (i.e. AJAX page load), it works for the same changes.
Reproducible at least on "insert record" and "create table" pages. On both latest chrome and Firefox on Ubuntu.
Fixed with https://github.com/phpmyadmin/phpmyadmin/commit/af08e1417e7a3ae8e0df5faf8a5db2f11343e9f5