It's not PON thats why they are able to provide 25 Gbit/s. And they choose 25 Gbit/s because the switches for it where only slightly more expensive than the 10 Gbit/s version would have been. They did a talk about it some time ago.
True but the "state owned ISP" in Switzerland only has XGS-PON hardware. So Init7 could only provide 25Gbit/s in the parts of the network thats not PON.
https://www.youtube.com/watch?v=wXmJCzMeIBo