cabal update doesn't respect index-state?

**Describe the bug**
I have a `cabal.project` file containing
```
index-state:
, hackage.haskell.org 2023-03-16T09:32:28Z
, head.hackage 2023-02-16T05:32:02Z
```
but running `cabal update` in CI is showing:
```
Downloading the latest package lists from:
- hackage.haskell.org
- head.hackage.ghc.haskell.org
Package list of head.hackage.ghc.haskell.org has been updated.
The index-state is set to 2023-06-09T14:04:13Z.
Package list of hackage.haskell.org has been updated.
The index-state is set to 2023-06-17T22:28:17Z.
```
Is this expected?

I'm using the scripts from `ghc-wasm-meta`, which installs `cabal-install-3.10` and [this `cabal.config` file](https://gitlab.haskell.org/ghc/ghc-wasm-meta/-/blob/master/cabal.config)