I am located in the Ardennes and uphill my Honda seems to struggle a bit. No big deal.
Of course the ICE revs go up when going uphill or otherwise demanding "more power"!
Where do you think, the power comes from? - The higher the power demand, the higher the revs of the ICE!
It takes a little time to get used to a full-hybrid's behaviour because the ICE normally is completely disconnected from the wheels. So, there is essentially nothing you can do about high engine revs besides lowering your power demands.
Addendum:
The (facelift) MK4 Jazz's ICE provides its maximum power output of 79 kW between 6000-6400 upm.
So, whenever your driving requires maximum power, your ears will bleed
