There are satin finishes and satin finishes. The cheap satin finishes, such as those used by Martin et al are just lacquer with an added ‘flatting’ agent - I think it’s called catalysed lacquer, but I could be wrong - and those do shine up where arms, hands etc. touch, and it can happen pretty quickly - within a few weeks or months even.

Satin finishes such as those on Lowden guitars are in a different class - they are ‘normal’ gloss lacquer which is ‘knocked back’ by hand-rubbing with finer and finer grades of abrasive (wire wool, IIRC), and they don’t shine up as easily, if at all.

My Lowden O-25 had little or no shine in those spots after seventeen years of regular play, and my F-23 has zero shine after seven years.