Two years in the SIU would mean earning far less money than the license you earned through rigorous examinations and qualifications would get you. It would also be time lost towards advancing to 2nd Mate. The only people I ever knew who sailed AB were folks with MSC waiting for licensed positions to become available or those wanting to get a PIC for tankers.
Ask yourself: Would two more years of doing the same exact work you did on deck on summer sea terms make much of a difference? Is chipping rust, powerwashing and swabbing decks, mucking roseboxes, painting and taking trash out going to make you a more confident and competent watchstander at sea or in port? You’ll find yourself right back on MUG cruise as a watchstanding AB - standing there looking at open ocean and calling things in… and making coffee/keeping the refreshments area clean and orderly.
Trust me, you’d hop on a ship as AB and see some green 3rd Mate stumbling once or twice but rapidly getting the hang of things, which will just make you angry and bitter as was mentioned above. Sounds like whoever this person is either had no choice but to take that road to advance or they are trying to deter would-be competition from taking jobs they want. I don’t know, I am not a member of that group and cannot see the post.
If you worked hard like you say and feel ready to roll - I’d dive right in. Two years unlicensed shipping in SIU after school would be a colossal waste of your time and education.