Backers refers to someone who contributes to a reward-crowdfunding campaign. You're either donating some money to get a reward or essentially, pre-buying a product. So, you're supporting/backing a project -- hence, a backer. They did offer "pre-orders" for a product not fully developed and that is not shipping until 2021.
Investment crowdfunding is a way to source money for a company by asking a large number of backers to each invest a relatively small amount in it. In return, backers receive equity shares of the company.
Amico has effectively done both.
You're right... Retro, casual and non-gamers are most likely not going to buy a Series S. Why would they when the Switch is the better choice at the same price? It's market place is full of casual sub $5 games and of course most of Nintendo's classic games and more than couple "Collection" series from a few of the old school companies to pull in the retro crowd. And far, far better 3rd party developer support. I'll give you that Tommy carries a lot of weight in the gaming industry and is highly connected... but I'm not sure that's enough. I would absolutely love to be wrong about that, but I just don't see the long term value in an Amico.
As for this retro/casual gamer... nope not buying the Series S...
Gonna pre-order the Series X.
For me the Amico is just an interesting collectable.