There are two challenging things here that makes this a discovery. One, making the material, which is extremely difficult to verify as altermagnetic due to the nature of measuring these materials. Two, the measurement, which combines two techniques to distinguish this as separate from antiferromagnetism.
It is a huge push forwards for the budding field since it provides a really nice way to go to a large-scale synchrotron with your altermagnet and study it in detail.
This would have to scale down to the quantum domain to be an actual thing and scaling back up means we bring non-commutative physics into the classical world.
Also, do you have a link to the arxiv post of 2021? It's a lot of time. This article looks like studing how to "see" the pattern. Perhaps the old one was about the material and general properties.
From 2021:
https://arxiv.org/abs/2105.05820 This is the numerical discovery.
I'm trying to decide if we are intentionally 'translating' these ideas from pure imagination down into technological applications through intermediate 'realms' of quasi-reality, or if building stuff with just intuition can still be accepted in the 21st century. The BS is just piled too high for me and my trust in technology is not great. Sometimes I wonder if we are just having a mass psychosis in a field of mud.
IIUC the new article is about taking a "photograph" of the magnetiation in a real sample, and the old article is a theoretical prediction. Perhaps the new article should be presented as a confirmation instead of a discovery, but press releas are full of omisions and overhype.