Having too much metal is not operative - and in any event all they would need to do is ETD on it to clear it.

This falls under TSA's "What Can I Bring" category of Household and Tools.
Corded electrical appliances without batteries (such as hair curling irons, microwaves, blenders, fans, etc) are specifically permitted by TSA in checked baggage with some minor limitations if it has blades or other sharp objects. It might also be permitted in carryon but there are some size limits. In addition, individual airlines might have restrictions separate from TSA's limitations.

I suspect s/he/they were confused and believed, in error, that it was (or contained) an actual battery that exceeded the allowable size. You should contact the airline and also TSA for clarification if you are thinking or would like to travel with it again.

What Can I Bring? Household & Tools | Transportation Security Administration (tsa.gov)

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