Much of Windows 11 development is validated by users in the Microsoft Insider Program. This allows access to new features before they are released, at the same time they are being tested and evaluated.

Microsoft now wants to make more changes to this software and change the development philosophy. This method will continue to get access to the news, but it will also separate the developer and beta channels, now it’s time to choose the channel and change.

Insider program with many changes
There are not many times that Windows 11 Insider development channels are aligned.  These follow different architectures, with different developments and with novelties also separate and progressing over time.
Microsoft has now slowed its developments in buildings with a clear purpose.  Adapted development channels so that users can switch from developer to beta, ensuring greater stability in systems.

Hey guys - we have something new # Windows 11 building for #WindowsInsiders On Dev AND Beta channels today.  Check all details including the limited window to switch between flight channels - https://t.co/hgeWk8pcwa ^ pic.twitter.com/S6yq5uUAN8
Windows Insider Program (windowsinsider) March 23, 2022
Microsoft will change Windows 11 even more
This is a unique opportunity, as the developments of this Windows 11 software will soon follow very different and parallel paths.  Thus, it gives users the possibility to choose a new development line.
Microsoft wants the Dev Channel to be the place where its programmers test ideas and concepts that may never materialize in Windows 11. The Beta Channel will be the point where the following news is evaluated before it is delivered in updates to this system.

It's time to choose a Dev or Beta channel
The change should now be made directly in the settings.  Here, you have to choose the Windows Update option and then the Windows Insider Program to access the options.  Simply select the beta channel to switch.  Microsoft indicates that this change can be made later with a clean install.
This is an interesting and very important change on the part of Microsoft.  You want to make room for Windows 11 developments and that's why you now have these two Insider Channels.  Dev and Beta will follow different paths with very different philosophies.