I agree that it's important to avoid the reintroduction of too powerful faction options for armies.
However, our update contains stupid things.
Let's consider the battle tactic Stampede of Scales. It's similar to Ferocious Advance, but it's still different and certainly it's not unbalanced. You can effectively choose between the 2 tactics, you can even complete both of them in different rounds. It's a balanced additional tool.
But the Grand Strategy Astromatrix? you pick 1 strategy in a battle, and Astromatrix requires a wizard alive, placed in a certain position, without a enemy wizard in another position. The core Grand Strategy "prized sorcery" requires just a wizard alive.
There's no comparison, there's no choice. No one will ever take Astromatrix over Prized Sorcery.
The fact that both of those grand strategies exist is indeed stupid. So I'm going to assume whomever wrote Astromatrix just forgot "prized sorcery" was a thing. Either that, or they forgot to actually add in an advantage for Astromatrix to balance out the disadvantages. Which seems realistic given the kind of mistakes GW regularly makes.
It's such a shame though, cuz the the idea behind astromatrix is at least interesting (assuming prized sorcery didn't exist to ruin it

). It's also about the only rule in the update that's actually somewhat fluffy and shows some semblance of originality.
And yeah, for basicly all the stuff in our update there's no real choice.
Astromatrix, in its current form, is just a worse "Prized sorcery" so why ever take it?
Thunderquake is underwhelming at best, so building an army around it is pointless. On the other hand, if you play thunderlizard you probably have the required troops anyway so you might as well get the free battalion. Either way, the choice is kinda made for you as it's an auto include/exclude and not something you build towards.
We finally get mount traits, but only 1 per subfaction, so again, there is no actual choice to be made you just take whichever is allowed in your subfaction.
It makes it a very lackluster update, even if objectivly it still makes our army better cuz none of it makes for an interesting choice, or even an interesting impactfull new ability.