Actually "having friends" is the problem. The report is clear, SB was already in violation of NCAA rules as soon as he continued communication with the parents after taking the job. Would he have been caught if they hadn't transferred? Probably not, but that's not entirely the point. Per the NCAA's own interpretation of the bylaws, a coach is not allowed to communicate, at all about anything, with the parents of an athlete for another school. Here is the relevant section of the report:
Bylaw 13.1.1.3 (2022-23 NCAA Division I Manual) addresses tampering. The bylaw states that an athletics staff member shall not communicate or make contact with a student-athlete from another NCAA Division I institution, or any individual associated with the student-athlete (e.g., family member, coach, advisor) either directly or indirectly, without first obtaining authorization through the notification of transfer process. Stated differently, no communication can occur before the student-athlete enters the transfer portal. [...] the bylaw does not make a distinction between recruiting contact and non-recruiting contact