Hi @Patrick_Jakubik,
I can confirm that this is expected behaviour, metafields added to a Draft Order do not automatically carry over to the Order created from the Draft.
You can create a metafield definition sync to pass a specific draft order metafield definition to the created order via the Admin, though it’s not currently available via the API at this time.
I have also discussed this behaviour further, along with some suggested workarounds to capture Draft Order metafields and create them on the created Order via webhooks, in the following thread for context: