That is horrible advice, especially to someone that has a 3AD scholarship. If you enlist, you will have to leave the USAR/ARNG in order to contract your sophomore year for the 3AD scholarship. The USAR/ARNG needs to release in order to do so, and they are not obligated to release you. You will need to get a conditional release which takes a very long time to get approved, if it even gets approve. Don't ever enlist to SMP if you have a national scholarship prior to ROTC contracting. You may enlist after contracting with ROTC and having the scholarship converted to GRFD. You are only an SMP cadet once you have contracted with ROTC. If you enlist as 09R, and if they don't release you, then you have lost your scholarship. They will also schedule you for basic training after your freshman year of college.
You don't have to tell me your school/ROTC program, but what was the position of the cadre member who told you that?