It is a normal behaviour for this sample.
If you open https://github.com/cuba-platform/sample-google-map/blob/master/modules/web/src/com/company/sample/web/screens/map/MapScreen.java#L96 then you will see call of GlobalConfig.getDispatcherBaseUrl(), this URL must be properly configured on production if you want to use it.
Usually we recommend to set cuba.webAppUrl ,cuba.webHostName, cuba.webPort and cuba.webContextName (see the list of common properties here: https://doc.cuba-platform.com/manual-6.4/app_properties_reference.html)
This behaviour is applicable only for this sample, not to the Map itself. If you want to set up your server with this sample properly - set these properties: cuba.webAppUrl ,cuba.webHostName, cuba.webPort and cuba.webContextName according to your server parameters.