There's no info about this freebie on the website linked - is it just the flier?
No way they will ever force you. If they did I will just keep breaking it.
Some reasonably objective views here: https://www.theregister.co.uk/2018/11/23/smart_meters_are_dog_toffee_says_nao/ As always, The Registers article comments are usually worth a read too.
They are still allowed to install 1st gen smart meters until April 2019, they are just trying to install poo in to your house. 1st gen will only work with SSE,so if you move provided its useless, and they keep all the data they have collected about you.
Out of interest how much electricity does a smart meter use? Googled it....... about a £1 per year