It seems there might be a change in interpretation. I just got an email intending to clarify the "it's ok to switch devices" policy stating:
"Take it two at a time — Feel free to install Evernote on as many devices as you like. If you’re on a Basic account, you can log in from up to two devices at a time. Need to switch devices? Just log out from one and log in on the other."
However, this is a misrepresentation of what recently happened to me. I logged onto my Basic account - sometime yesterday, I believe - and got a notice that if I didn't immediately REMOVE Evernote from the other (more than 2) devices, my account would be closed. No mention at all of signing out.
At the time I was on my computer (device 1) and my phone (device 2). My tablet was not turned on. The 4th device was my (same) computer which had been reformatted so that "device" hadn't been accessed in months.
It seems the new policy in practice isn't fitting the stated policy.