I think they weren't saying that it's not an apt metaphor, but that it's not a good one, because now you first need to explain to people why regular debt is not

I think they weren't saying that it's not an apt metaphor, but that it's not a good one, because now you first need to explain to people why regular debt is not necessarily bad, before being able to move on to your actual point that technical debt is also not necessarily bad.