User-agent setting from config.xml does not work

I am setting user-agent through preference tag in config.xml file for android platform
<preference name=“OverrideUserAgent” value=“Mozilla/5.0 My Browser” >
<preference name=“AppendUserAgent” value=“My Browser” >
When running the app using ionic serve command I do not see the above mentioned user-agent value in the request headers (Dev tools -> Network tab ->Request headers). user-agent has value like “Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36”

Correct user-agent value is needed to pass the validations on the server side.

Am I missing anything?

Can you fix that? That is a ridiculous way to validate clients.

It’s a REST API maintained by third party that needs user-agent value.
Documentation says it’s possible to set this value. Any thoughts why it’s not working?