index.RelatedFields example contradicts following documentation

[ssyberg]

index.RelatedFields documentation shows an example with a nested FilterField and then in the very next section says the example does not work.

Pertinent section of the Wagtail docs

Two related sections:

• https://docs.wagtail.org/en/v5.2.3/topics/search/indexing.html#index-relatedfields
• https://docs.wagtail.org/en/v5.2.3/topics/search/indexing.html#filtering-on-index-relatedfields

Details

I don't actually know which section is incorrect, the example or the documentation contradicting it. Here we have an example showing a FilterField in a RelatedField:

Then the very next sentence states:
"It’s not possible to filter on any index.FilterFields within index.RelatedFields"

Perhaps there's some other reason to declare a FilterField within a RelatedField but if so I think that should be clarified right here.