The No Load Flag sets a configuration variable that the utag.js file looks for. If the no load variable is true then the utag.js file skips over all the code that loads other tags. Essentially if you enable the No Load Flag the utag.js will still load on the page, but none of the code will run within the file, which also means none of the tag vendors will load either.
The utag.sync.js is a separate file that doesn't take into effect the No Load Flag. This file will still load and run as it did before enabling the No Load Flag.