We do not yet support ordered collections via @OrderBy.
I initially thought that'd be handled by ORM internally so we'd benefit from it, but actually the specified order columns are appended to the WHERE clause of the collection fetch statement.
We could do the following:
Expose the order column(s) through association context to getAssciation() so dialects can apply the ordering upon fetching as well
If a dialect indicates that it doesn't support ordered fetches, we'd apply the ordering in core as a fallback