He would never have faced a perjury charge as you have to lie in court/under oath
If he’d have gone to court and denied it, and it was found that he was actually driving that day, then yes, he would have faced a perjury charge*. I’m guessing he knew that he was done for, especially with all the phone recordings and saved text messages, so he pleaded guilty.
what you say anywhere else is beside the point.
Indeed, so he didn’t deny it in court.
*EDIT: Well, there’d be grounds for one…whether or not he’d be charged with it, I dunno.