Email list size for Kickstarter??

I used Thomas’ business plan generator to help me think through next steps and a plan, and it suggested that I use Kickstarter to launch my first book (which I’m good with, it seems like the most sensible way to do it). However, it recommends starting an email list just months before the Kickstarter launches.

Now, I already have a (miniscule) list, but I’ve been delaying launch for the sake of building up that list. Should I continue doing that? Is there a certain size/engagement level that I should be looking for before launching, or do you just go for it and make it happen as you go? I’m just wondering what’s the wisest course of action because
1. There’s a lot of talk around publishing about numbers (I know, it’s not all helpful and some is just an excuse).
2. I worry that not hitting a threshold will mean I struggle to get the word out (I don’t use social media)
3. I worry that trying to hit a threshold is just an excuse to faff about procrastinating
4. I worry that even putting a number on it is a moving target

This particular book is a novella that is the full story of a short that was published in an anthology. It did really well and was spcifically mentioned in a number of reviews. I also have a list as long as my arm of places that I plan to reach out to and pitch to publicise the kickstarter. I’ve run it by people who actually know about that sort of thing and it appears to be a solid marketing plan.

I guess I’m just looking for advice: do I continue with my plan of focusing on building up platform before launch, or just go for it because I already know people liked the story and I have a solid plan? And if I wait and build up more of a following, how long and what should the goal be? Or am I just overthinking the whole thing and being a chicken and need to just choose an option because both are fine?

Edit: I also asked AI Thomas just now.