Yes, I noticed that as well. Some things had links and others didn't. Those new ones I assume will get linked once the 2025 MM is available.
We were discussing these name modifiers earlier in this thread and pondering whether all monsters would get these or just some and whether or not these were direct replacements for old monsters.
The example we discussed was the "bugbear warrior" in the Uni and the Lost Horn adventure is quite a bit different than the 2014 "Bugbear." So the question was is the bugbear warrior a new type of bugbear (like the 2014 bugbear chief) or replacement for the 2014 standard bugbear.
I speculated these new names mean new monsters and are not replacements of old monsters, and this bit of evidence from the DMG seems to support that theory to me. However, we will find out for sure in 1 1/2 months!
Edit: Here is what
@Kobold Avenger is talking about. Notice the bold red below is linked to the stats in the 2024 free rules, while those in bold are not linked because the presumably go to the as of yet unavailable 2025 Monster Manual (though I guess the links will not work if you don't own the MM).
View attachment 389844