If I'm not mistaken, you need to open two of the ports 80, 443 and 6667 to gain the Exit flag
It's in dir-spec.txt as such. Probably under some rationale of making nodes most widely beneficial. I'd think soaking up btc traffic would be useful, if exit traffic stats supported that need... is it 20GB per thick btc client now?, plus ongoing...
but not having that flag doesn't mean that you're not an exit Try waiting some days to see if there's some traffic on port 8333.
The atlas graphs do show traffic for such nodes providing essentially just 8333. They're usable manually, just not automagically by the client I think. I forget how their traffic is picked up.
There are 850+ nodes allowing 8333.
Have you considered running an onion:8333 seed node to both serve btcnet and keep traffic off the exits? There's an index on bitcoin.it for those. And iirc the btc client will learn them over the btcnet then use them within tor.
What is the motivation?