I'm not real warm on the inside paint, either. Why even chance it? I've used hi-temp paint on the outside of several cookers with good results. However, on the inside, if nothing else, you've got "grease and grime" to retard or obviate any rust issues. It's part of the seasoning -- a good thing.
When I got my NOS Traeger there were several spots on the inside bottom of the drum with no paint at all. After several cooks they've disappeared, covered by the natural coating that will always be there unless I use industrial-strength degreaser on it.
Hub