I search and found nothing about the windows update icon in Windows 10 RS3 Professional ... except maybe you used "Tweaks - Classic GUI - Enable Classic Windows Update UI" ?
Could you please check in EX-100 "Tweaks" tab if you activated this component ?
I added the automatic removing for this icon (even if you previously used "Tweaks - Classic GUI - Enable Classic Windows Update UI").
There are 2 conditions : - you need to set to "ON" : "Settings - Update and Security - Windows Update" - you need to remove : "Services - Windows Update Service"