Who says they haven't touched a computer for years? There's no requirement for your beliefs to be consistent. Otherwise there wouldn't be a single religious person left in the world. You can interview on a computer and reveal your religious preferences on the first day of the job.

There are a lot of weird ways interviews are done. I wouldn't be surprised if someone's interview process didn't screen for is someone even an engineer.

Though nothing about the Amish prohibits being a computer using engineer. Their rejection of technology is a lot more nuanced.

Because he was hired when the company still used typewriters.