It's not about sending different icons, but about recieving the right one. There can be 2
If the fonts aren't there, they will be replaced by an alternative font. This can be the case if the os has restrictions for receiving ttf files.
Or when old fonts are cached in the browser, the framework will use them and there will be new call at all to the server. This behavior you can check in the networking tab. Removing the ttf files in the browser cache mostly solve the problem.