Node-Red nodeJS upgrade 8 to 10 or not sometimes

I know this is likey a daft question but..

I just created a clean Raspbery Pi and used your upgrade script to install Node-Red - it put in NodeJS 10.x

But then I tried to use it up upgrade a working (up to date apart from NodeJS) system - with NodeJS 8 already in it - and the script did little or nothing - came back almost straight away - and nodeJS 8 is still there. Is there a way to tell it to go for NodeJS 10 ?

First Pi nodejs -v = v10.15.1
Second Pi nodejs -v = 8.15.0

If it's on 8 which is LTS and we know works well - we don't force it to 10. If it's empty or pre 8.11.1 we do install 10.

As you know well forcing things from one major level to another means all your extra nodes may need to be recompiled... eg serialport etc - which can cause many bumps.

Can a user choose to upgrade to 10 with a command line switch?

Not via the script