OK.

From Wikipedia.

Alpha

The alpha phase of the release life cycle is the first phase to begin software testing (alpha is the first letter of the Greek alphabet, used as the number 1). In this phase, developers generally test the software using white box techniques. Additional validation is then performed using black box or gray box techniques, by another testing team. Moving to black box testing inside the organization is known as alpha release.[2]

Alpha software can be unstable and could cause crashes or data loss. The exception to this is when the alpha is available publicly (such as a pre-order bonus), in which developers normally push for stability so that their testers can test properly. External availability of alpha software is uncommon in proprietary software. However, open source software, in particular, often have publicly available alpha versions, often distributed as the raw source code of the software. The alpha phase usually ends with a feature freeze, indicating that no more features will be added to the software. At this time, the software is said to be feature complete.

Beta

Beta (named after the second letter of the Greek alphabet) is the software development phase following alpha. It generally begins when the software is feature complete. Software in the beta phase will generally have many more bugs in it than completed software, as well as speed/performance issues. The focus of beta testing is reducing impacts to users, often incorporating usability testing. The process of delivering a beta version to the users is called beta release and this is typically the first time that the software is available outside of the organization that developed it.

The users of a beta version are called beta testers. They are usually customers or prospective customers of the organization that develops the software, willing to test the software without charge, often receiving the final software free of charge or for a reduced price. Beta version software is often useful for demonstrations and previews within an organization and to prospective customers. Some developers refer to this stage as a preview, prototype, technical preview (TP), or early access. Some software is kept in perpetual betaGÇöwhere new features and functionality are continually added to the software without establishing a firm "final" release.

Open and closed beta

Developers release either a closed beta or an open beta; closed beta versions are released to a restricted group of individuals for a user test by invitation, while open beta testers are from a larger group, or anyone interested. The testers report any bugs that they find, and sometimes suggest additional features they think should be available in the final version. Examples of a major public beta test are:

Open betas serve the dual purpose of demonstrating a product to potential consumers, and testing among an extremely wide user base likely to bring to light obscure errors that a much smaller testing team might not find.

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OK. So as you can see, alphas have stability issues, data loss and crashes. Sounds familiar. Invalid fittings, anyone? Hard lock, anyone?

Betas are used to test software that is feature complete - read and understand what that means. It means that core functions are ready, but need volume stress tests to identify bugs that cannot be identified internally by the developer due to not having the ability to generate large volumes of test metrics. This is achieved by open or public beta, or by controlled closed beta.

What we have with dust, is software where the core functions are still being refined, but the developer has chosen to move to beta stage despite stability issues in the core which technically mean that what we are testing is a later variant of an alpha build.
The reasoning for this is simple, the software is not yet feature complete, so by definition, it cannot be a beta.

That's going by the book of sdlc.