Speaking as someone who’s been trough that, I don’t think that the article gives a complete picture. Part of the problem appears to be (particularly by reports from newer generations) in such instaces is the feeling of unreality, as the only times when we tend to see such situations is when we’re sitting comfortably, so a lot of us are essentially conditioned to sit comfortably during such events.
However, this does tend to get better with some experience of such situations.
Egan’s stance is not materialistic in the least. It can be best described as a “what if” of extreme idealism. It has computers without any substrate, as well as universes operating on pure mathematics. You can hardly find a way of being less materialistic than that.
The idea of singularity and AI originates with Stanislaw Lem. Vinge was following his lead.
Egan’s novels do have plenty of themes relevant to transhumanism, though their underlying philosophical suppositions are somewhat dubious at best, as they negate the notion of material reality.