Never believe what you read on some random person on the internet's blog. It's junk. Go to the source. All you had to do was visit the Google Voice help forum to understand what's happening.
Google has been pouring piles of money and developers at Google Voice for the past two years. The entire infrastructure has been replaced (servers, network, carrier routes, etc), the iOS and Android apps have been replaced, the website was replaced. It's a greatly improved service now, with current and future development focused on VoIP, not PTSN improvements. Note that the migration of OBiTALK devices from XMPP to SIP was part of this effort. Inbound calls, for example, now forward to Android and iOS clients, webpage clients and Polycom OBiTALK clients on the same VoIP infrastructure.
The most significant change since the service was first offered has just now finished rolling out to all users: no more need for Google Hangouts; you can now make and receive telephone calls over the Internet (WiFi/Ethernet/4G VoIP). There is no longer any reason to use Hangouts for calling or text messaging.
As part of that change, the default on the Google Voice website is to now use your browser to make calls over VoIP. If you don't want that, then simply go to Google Voice settings and toggle the switch to go back to the carrier-based method. If that setting is currently grayed-out for you, then sign out of your Google/Gmail account, clear the browser's cache, cookies and history, close and reopen the browser, and try again; it may take another day for it to be activated.
READ: https://support.google.com/voice/answer/7649189?hl=en&ref_topic=1708123
