There is two possible explanation why AMD changed that at SMT2
Why is this still discussed? AMD have already said they don't plan smt4 for Ryzen 3. I don't think that it where their bottleneck is. I don't think they will gain much by doing that, especially when they have an amazing system for churning out more cores.You seem pretty confident that SMT4 isn't happening with Zen 3. So how much money would you bet on that? Would you bet your annual income that Zen 3 isn't SMT4? Are you so confident still? Probably not. It's easy to be hero behind keyboard without any responsibility.
My bet is 60:40 for new wider and/or SMT4 core for Zen 3. It's doable, technology is already developed by others, risk is minimal, AMD has great engineers and they had time to do that. All the puzzles shows AMD is hiding something about Zen 3. The only really confident people about Zen 3 SMT are AMD engineers. Everybody else confident is just keyboard hero.
We know for a fact that it will have a unified L3 cache, we know it will have faster gates, better branch predictor and smaller latency between cores. They might actually do some sort of L4 cache as well, to improve flow and feed the cores faster.