TN visas are not for software engineers, they are for software analysts, or actual engineers. And they are not dual intent (you can't convert them to a green card).
1. The are plethora of examples online people holding TN work as a SDE with a CS degree
2. I believe you can file to change intent 90 days after entry
Job titles are at some level made up.
Try using that argument with a xenophobic highschool dropout immigration official...
Are there any highschool-dropout immigration officials in the US? I kind of doubt it.