So you've been in the country illegally since you were brought to the US on a tourist visa as a child? You went to undergrad and law school but never asked them to sponsor a student visa? but now, your LPR application from marriage is absolutely fine, despite having been in the country for years illegally??
This seems really, really unlikely and doesn't add up.
You should probably read up on the INA before you fly into these types of threads accusing people of lying. It makes you look like an idiot.
Why do you imagine he'd ask his UG or lawl school for a student visa? What good would that have done him? Student visa is a nonimmigrant visa, in case you were unaware (and clearly, you were) and nonimmigrant visas require you to demonstrate that you have no intent to remain in the country after you're done with your studies plus the one year long work authorization you get with the visa. How do you imagine this guy would prove 'no intent to remain' under his circumstances? No immigration authority worth its salt would grant him that visa.
On the other hand, a Green Card by definition allows you to have an intent to remain. All he needs as a marriage-based Green Card applicant is to show that he's entered into his marriage in good faith and not solely to obtain an immigration benefit. If he can demonstrate that, he can adjust to a lawful status (assuming no criminal record or other inadmissibility grounds). He can't travel while the application is pending because he'd trigger the readmission bar if he left, but he can certainly hang out in the States and volunteer at his 1L internship while the whole thing gets straightened out.
TL; DR: his story makes perfect sense. Go learn some immigration law before wielding accusations.