@Rod
Yellow tips of needles more than 12 months old is not a big deal.
However, if my eyes are not deceiving me, in this most recent photo, some of this year's current growth has yellow needle tips. That is not good, that is a sign of issues, possibly insufficient roots, or an episode of drought? It could also be a sign that you should inspect closer for insects. Though I can't see any obvious insects pests. Just take a good look and evaluate., Yellow needle tips on this year's current growth is a warning sign something is wrong or if not wrong, less than ideal.
Will it be strong enough to work on in spring 2024? If you have "blue shiners" everywhere, meaning lots of nice bright blue healthy buds, multiple, meaning 3 or more, buds growing on every branch tip, then you are good to go. If you only have ones and twos on the strongest branches, and the yellow needle tips have gotten worse than this photo, then your tree will need an additional growing season to recover. Check back to these photos when deciding in 2024.
With spruce, if you are not sure, it never hurts to give it another year to recover. They are slow trees to work with.
About inverse taper. With blue spruce, almost ALL of the blue spruce sold that have bright blue foliage are grafted trees. Your tree is bright enough that I would guess it was grafted. If it had a cultivar name in single quotes when you bought it, for example Picea pungens 'Blue Pearl' or 'Fat Albert' , the name in single quotes would be the cultivar name of the scion grafted onto the understock. The understock could be anything, often it is just a common seed grown blue spruce, but it could be any of a dozen spruce species used for understock in commercial nurseries.
Seed grown blue spruce will often be green to gray in color. The much sought after "blue color" is really only a one in 1000 occurrence when grown from seed. There are seed strains that are somewhat blue, but yours seems blue enough that I suspect that your zone of "inverse taper" is really the graft union. Is this a fatal flaw as bonsai? Not at all. Bill Valavanis has or had a wonderful blue spruce he displayed for many years with a noticeable graft union. It was well healed and not too distracting, so it was accepted as unavoidable in this type of tree. So my advice would be to ignore the inverse taper, or if it really bothers you, train a branch to have a little foliage cross the trunk at the right height to hide the graft union.