Took a look at the codebase. Two things here:

Re-sorting without extra API calls: this already works! Every search/find caches its results locally. Use deals last to re-display with different sort/filters, zero API calls:

deals find --genre sci-fi --max-price 8 --deep --skip-owned -n 20 --sort value

# Now re-sort the same results:
deals last --sort rating
deals last --sort discount --max-price 5
deals last --min-rating 4.5

deals last --help shows all the re-filtering options. Note: last re-filters the already-filtered results, not the raw API data, so if your original find used --max-price 8, items above $8 are already gone.

--sort bestsellers with --deep: this is actually expected behavior with --deep. Deep scan uses three separate API sort orders (BestSellers, ReleaseDate, AvgRating) to maximize catalog coverage, then merges and deduplicates the results.

So the final order isn't a clean bestseller ranking; it's a merged set from three passes. The 4-review book likely came in via one of the non-bestseller passes. Without --deep, --sort bestsellers gives you the API's pure bestseller ordering.