in most of the cases IMS services like VoLTE and VoWiFi are dependant on agreements between operators and HMD Global. In general, before VoLTE/VoWiFi enable, it needs to be properly tested and approved by the operator first. This is done so that the operator can ensure the best possible quality of the given device towards their own customers.
Yes, seems as that is the mode of one mobile device model to be used/accepted with VoLTE/VoWIFI in your carrier network. But, if we are waiting for operator to request this from Nokia, in my case, maybe will be never.
My operator do not sale this model (Nokia 8) or another Nokia model, so maybe i will have VoLTE/VoWIFI never. They start with Samsung S8/S8+, Xiaomi Mi6 and ZTE Blade A320. Maybe continue with iPHONE's and so on. I'm a little bit disappointed with Nokia 8, i suppose will be a real alternative to Samsung S8 but seems as Samsung is more implicated to collaborate with Mobile Carriers as anyone else.
I think that Nokia would be less than popular with carriers, if they started enabling it without the acceptance from carriers.
As far as I have understood it, Nokia cannot do anything if the Carrier have not decided to support on the Nokia 8, so until your carrier tells Nokia to enable it for the specific Nokia model, it will not happen.