The person you're responding to must have meant as a child, but I can also provide an adult anecdote: I could understand spoken German sooner than written because I, well, never read the language (can't understand it anyway) but was listening to conversation at the dinner table of German family and so picked it up that way

I know someone who learned to understand German spoken on TV and would sometimes speak it themselves (on day trips across the border primarily I imagine), so they've got a good intuition for e.g. word gender (that their native language doesn't have) but they can write most words only phonetically and don't know the grammar. Thankfully German orthography is not like English', but it's also not a 1:1 map (cheese isn't kese; name arbitrarily has no h)

My parents spoke German when I was a baby, but switched fully to English when I could walk so that I would fit in with other neighbourhood children. I learned to read in English.

I can still understand sufficiently simple spoken German and decipher some written German. You could say I read it at the level of the two-year-old I was.

Typically, children first learn to talk (although it can be a sign language) and only later to read and write.

If they grew up born to German parents in a foreign country…