Can’t update software on my Apple Watch using cell network
Can I download software using my cell network instead of WiFi ?
Apple Watch SE, watchOS 10
Can I download software using my cell network instead of WiFi ?
Apple Watch SE, watchOS 10
See the 'Get ready to update' section in:
Update your Apple Watch - Apple Support
The third step says "Make sure that your iPhone is connected to Wi-Fi." so the short answer to your question is no.
Can’t update software on my Apple Watch using cell network