The classical definitions of alpha test and beta test:

• Alpha test is an internal, private test of a product unavailable to the general public, e.g. by employees of the company that created it.

• Beta test is availability of an unfinished product to the general public, possibly gated by some application / selection process to control the number and diversity of testers.

The terms alpha and beta have slightly different connotations in modern times, because of one product: GMail. It was essentially complete when it was released, but it was marked as being in beta for years even though it had a huge number of users. This led a large number of people to expect "beta" to mean something more like "essentially finished product which may have minor tweaks and polish."

If we talk about Steem and Steemit, it's definitely a beta in the classic sense -- an unfinished product available to the general public. But the sorts of changes it's still undergoing are perhaps beyond the expectations of some people who are using the post-gmail definition of "beta," so it might