Bill got the information in interviews with Haist and from his book. He fully cites his references with credit to Haist. The pH 10.5 fixes were known for years and used by Kodak in the P-122 and Xomat processes.
The emulsion swells, but does not become more fluid, just as a sponge does not become more fluid as it swells. It merely contains more water and this can be measured using a swellometer. As far as stability goes, no, archival is not alkaline. The atmosphere is mildly acidic and oxidizing and the wash water is nearly neutral so the final pH after wash will be close to neutral and swell will have decreased thereby. As it dries, swell goes back to nearly the same value as before processing.