The formation is alloyed (the linemen in the back field would need to report as eligible) but what the punt team does is not. In the NFL, the ineligible receivers are not allowed down field until the ball is punted, where in college the entire line goes down field while the 3 linemen in the backfield stay back and block. If an NFL team did it, it would be a penalty for ineligible down field.
To be more clear, in the NFL the kicking team (with the exception of eligible receivers) cannot vacate the nuetral zone until the ball has passed the line of scrimmage. In College, everyone can immediately release at the snap in coverage (the caveat would be if a forward pass was thrown illegal man down field would be flagged). The spread punt formation essentially allows the coverage team to start in it’s lane like a kickoff and requires the return team to cover them so they don’t get a free run at the returner.