Hi Eric,

I’m very impress by your dedication for all these years and understand you wanting to protect this beautiful tree. It must be gratifying to see it at 12 feet tall now.

It seems that a Giant Sequoia can withstand temperature of -30 degrees but the root system is somewhat sensitive because it is close to the surface.

We must then protect them from freezing with a thick brush or mulch layer and also protect against ice wind with a tarp or burlap (as you’ve had done in previous years). Source: https://en.garden-landscape.com/giant-sequoia-sequoiadendron-giganteum-care-instructions-8834#overwinter

Another website says that young sequoias are not very sappy and are subject to freeze-drying. Keep them watered up until the ground freezes. If possible bury the tree in snow because in their natural environment they are buried in snow all winter. So you may want to construct a windbreak when there is no snow. The cold is not the problem; the cold dry wind is. Source: https://www.giant-sequoia.com/faqs/giant-sequoia-landscape-questions/

The National Parks Service says that Giant Sequoias need well-drained, sandy loam to support their expansive root systems and that winter snow melting slowly provides a steady supply of water. Source: https://home.nps.gov/jomu/learn/nature/john-muir-s-sequoia.htm

Forestry.com says that once established, they are relatively drought-tolerant and mulching around the base of the tree helps to retain moisture and suppress weed growthy. https://forestry.com/trees/giant-sequoia-tree/

From what you say about your site, I recommend that you continue what you’ve done in previously. Try to provide some buffer against wind to keep it from drying out and see if you can wrap at least some of the tree or construct a wind barrier.
Do check periodically for rodent damage during the winter.

I also think applying mulch is a great idea. Please note that it is not a good idea to apply too much so that they form a “mulch volcano.” Mulch piled against a tree trunk can retain water which elevate the bark moisture content making it susceptible to decay. Mulch will degrade and compact which will interfere with the root ability to get oxygen. The tree will respond by growing a second set of roots within the mulch. This eventually will cause irreversible damage. A few sources about volcano mulch should you want to read more about it.
https://bygl.osu.edu/node/1494
https://extension.psu.edu/mulch-volcanoes-are-erupting-everywhere

Lastly, while you did not ask for this, but this article from the University of Minesota Extension has good information on what can damage trees as well as what damage looks like, etc. https://extension.umn.edu/planting-and-growing-guides/protecting-trees-and-shrubs-winter#how-to-reduce-evergreen-winter-injury-1264311

I wish you and your tree the best for years to come!