This is what the blog explains:
Changes to the Beta experience
Based on your feedback to have clearer definitions between channels, we have committed to updating how we use the new Beta experience to reflect what is coming to retail in the following weeks. With this, there will be a realignment of experience when Beta Channel Insiders move to the new Beta experience.
So it sounds like Beta Channel will become Beta Experience (actually with lower case e on experience). And yet, what's the difference?
"... to reflect what is coming to retail ..." pretty much explains what the Beta channel always did, with the proviso that not every new feature would make it to the public builds. Or, I might interpret this to imply that the "Beta experience" more closely replaces Release Preview? Hard to say. Is Release Preview disappearing? Last I read on this, Release Preview will continue to exist.
While Beta Channel Insiders can generally expect a similar experience after this transition, some may notice feature changes. Although these feature differences will be minor, users who are looking for the best continuity of all existing features should consider moving from the existing Beta Channel to Dev Channel, in preparation for the move to Experimental.
This is even more puzzling. It almost sounds like the new Dev Channel, now called Experimental, is more similar to the old Beta Channel? Otherwise, why would a switch to Dev give you "the best continuity"?
These changes were supposed to make the Insider program simpler. They are instead creating more tiers, not fewer, now with the Canary Channel splitting into Experimental (26H1) and Experimental (future platforms).
My cynical self suggests that these "changes" are deliberately meant to b mysterious, designed more to drum up renewed interest in the Windows Insider program.