That Reddit post is based on the Chinese patch notes for the December 14th update…
https://di.blizzard.cn/news/official/20231208/34091_1124539.html
It provides not only catch-up mechanics for the Helliquary and Legendary gear ranks, it also introduces a way to increase your likelihood of obtaining Legendary essences you’re missing.
That’s something I suggested back in September…
https://us.forums.blizzard.com/en/diablo-immortal/t/how-about-a-pity-system-for-missing-essences/228