Manufacturers often say nothing else needed, so what? Many times they are also full of crap I've found. I don't hesitate to work around their instruction if I see the need.
Antisieze virtually has no more body than that drop of oil, it will also leak no more. Haven't seen one do it yet. It is designed to squeeze out to not make a buffer. If the connection slips then crap connector as I have already alluded to by looking at the design. You yourself say good luck trying to pull pipe out of one so it shouldn't be a problem.
I've got 3 universal stainless cats installed in steel tube exhaust pipe with antisieze and no trouble. Tube in a tube installation, no flanges. Never retightened them once, been running for years. Not manifold type but undercar cats where entire exhaust pipe weight hangs on them along with front/rear engine movement since no flexjoint used in system.
I used to build heat exchangers 6 inches long up to 40 foot long for battleships and nuclear reactors using 100% stainless construction so I kinda know what it will do and not do.........there were specific steps to take coating sealing joints there if carbon steel used instead of stainless to connect pipes up to the stainless unit.
The corrosion of steel onto the stainless will still have a tendency to stick it after years of service. I've seen stainless to regular steel connections that were stuck together almost as bad as steel to steel to where some destruction of parts had to occur to separate them. The steel almost welds itself to the stainless.........
Now if you commonly take the joint apart, fine. But if you put it together with years in mind before it comes back apart? What you'll find is that even with antisieze on it there can be trouble getting it apart. It DOES lower the effort to do so though, where it shines best. Since starting to use it, I've never had to destroy or deform an antisiezed connection to disassemble it, and that's the way I like it. I use it on all exhaust pipe work and have never had any trouble with any loosening parts ever. Nuts and bolts come loose easy too even if they look totally corroded, they don't break their studs. Nice.