I would not assume that, no. Following accounts is fundamental to using Twitter; I absolutely think the majority of people using Twitter are logged-in.
With all the public officials on Twitter (and FaceBook) publishing "public-facing" information, I'm surprised both are allowed to be/remain walled gardens.
To do my business taxes this year I had to DEMAND paper form acceptance, which was begrudgingly accepted once I went, in person, to the tax authorities [they want you to provide all sorts of tracking JUST TO FILE STATE TAXES, under the auspices of "two factor authentication"].
As a technosophisticate that intentionally avoids email and doesn't carry a cellphone... I weep for what my public-interfacing world will yet become.