This is a weird thing to say, surely you already have enough information to look into the problem. At least you were gracious enough to let them mention the chat though.
Not for me to say, but I suspect the issue is more that they want an internal ticket to ensure the issue doesn't get forgotten. Asking for an email will mean that it goes through their normal support channels. FWIW, I've gotten really good service asking about edge cases like this in the past.