Assume nothing. In the majority of cases it will never be an issue, but, and its a big but, if you find yourself at fault in an expensive claim they will try to wheedle their way out of any liability on the tiniest technicality.I understand what you are saying abought changing from the original pads, but if the replacement pads are better I'd of thought it would be ok.
A bit like when your owners manual tells you the type and model of tyres to be fitted how many people follow these guidelines and just fit a different manufacturers equivalent. I will have to dig it out but I'm sure the there is no mention as to what brake pads are fitted.
I will ask my insurance in case they decide it's an upgrade.