This site states this specific framing directly in its own timeline table: reliable, dramatic changes this early — named as not realistic during the week 3-4 period.
Worth reading this carefully: this site isn't saying dramatic changes never happen this early, but that reliable, dramatic changes aren't realistic to expect — individual variation means some may notice more, most less.
This site pairs this "not realistic" note directly against its own stated realistic expectation for the same period — smoother morning breathing and less chest heaviness — worth reading both together for the complete, honest picture.
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