Is it technically a vaccine tho?
Of course, why wouldn’t it be?
A vaccine is a medicine which provokes an immune response against a particular pathogen in order to safely prepare your body’s specific immune system to fight that pathogen in advance.
Whether it’s the viral vector J&J vaccine or the mRNA Pfizer and Moderna vaccines, each of them do that by presenting a key SARS-CoV-2 antigen to your immune system. This enables your body to ramp up its defense against SARS-CoV-2 before you’re exposed to the actual virus. So if and when you are exposed, you’re much better prepared to fight it.