The present perfect is used in more than one way (Fenn, below, gives four usages ignoring subdivisions). There is the more 'normal', 'completed (or practiced over a period) at some time in the past', usage
these themes have [not] disappeared
but there is also the 'familiar, time doesn't separate us really' role
'By modeling it upon the Eroica Variations Beethoven has demonstrated
cf 'In modeling it upon the Eroica Variations Beethoven is
demonstrating how ...'
[first variant from Beethoven: The Emergence and Evolution of Beethoven's Heroic Style_Michael Broyles]
The term 'hot news perfect' is rather disingenuous, as the 'time doesn't really separate us' notion rather than 'in the last few years' is the controlling factor for this usage. [See A Semantic and Pragmatic Examination of the English Perfect_Peter Fenn, where Fenn refines McCawley's ideas. He suggests the term 'rhematic' for this usage.]
What seems to be the source of discordance here is the pairing of the different usages in the same sentence.