Do you know if this includes Google Fi as well? From what I can tell, they appear to share much of the same infrastructure. There's even a link to Google Voice at the bottom-left side of the screen of the Google Fi website.
I don't have much knowledge of how Google Fi works but what little I know makes me think that, yes, Fi and Voice are doing the same thing. If they are, then yes, a Fi number is on the exact same footing as a Voice number for port-out shenanigans.
One data point for why Fi and Voice numbers are the same: For a long time, hip-and-trendy apps like Uber and Venmo wouldn't accept Google Voice numbers because they show up in API calls as "voip." About a year after Fi became widespread, Google Voice numbers show up in services that provide information about phone numbers with a carrier of "Bandwidth.com/GV" or similar so now the apps can whitelist that carrier as "yeah it's VoIP but it's fine." If I test the number of someone who I know uses Google Fi--but did use that number with Google Voice before Fi, so I don't know for sure if this is valid--the information returned still comes back as Google Voice.
