It only counts as a redundancy site if the colony could survive without Earth. What's the minimum Martian colony size that's self sufficient? Self sufficient doesn't just mean the ability to create sufficient food, water, air, shelter, sewage, etc but the ability to recreate all of the necessary machinery starting only from your initial supplies and undeveloped Martian natural resources.

So many of the industrial processes that we've developed assume a huge interconnected network of supplies. To make Mars self sufficient you'd have to reinvent a huge chunk of the modern industrial system while also trying to keep your small population of colonists from dying. It's a monumental challenge with today's technology.