Cold brew tastes sweeter than the same leaf hot - what's actually happening?

Cold brewing the same leaf consistently gives me something rounder and sweeter with far less astringency, which I assume comes down to slower extraction of tannins at low temperature while other compounds still come through over the longer contact time.

What I'm less sure about is whether anything is genuinely lost rather than just muted.

Are there teas people here think are actively worse cold, or is it mostly a matter of preference? And does anyone adjust ratio for cold brew or keep it the same?