The digamma was never used in Homer's written form, but the poetic metre in some place is done such that there would be a digamma there and in some places, they don't modify the metre to adapt to the digamma.
There's a two-hundred year gap been it bring composed to capturing it in written form. It was in oral form and didn't written down (outside of some short fragements) for the ~200 year.
When the The Odyssey was composed, widespread use of digamma sound was still a big thing.
I can easily believe that anachronistic language was added in the process of writing them down, but the original audience wasn't people reading in a book; it was people who were listening to a poem that had never been written down.
There is a huge amount of anacronistic content, but when it was first performed, language was relatively contemporary at the start.
When the The Odyssey was composed, widespread use of digamma sound was still a big thing.
I can easily believe that anachronistic language was added in the process of writing them down, but the original audience wasn't people reading in a book; it was people who were listening to a poem that had never been written down.
There is a huge amount of anacronistic content, but when it was first performed, language was relatively contemporary at the start.