Yup, not uncommon in special applications.
Flux density most likely doesn't exceed 1.5T or so due to use of iron core materials; any external field is wasted effort that could've gone into the launch, and for something like this, it's a lot easier to just make a longer armature (thus more cross-sectional area A_e) than to increase field strength and cost massively on efficiency. (Flux density over 2T would leak out of the then-well-saturated core, and thus be wasted at least in part.)
Not that efficiency is necessarily a problem, in and of itself, but when it takes some GJ to launch a fighter jet, and you have only so many 100s of MW available onboard the ship -- there is a certain economic argument to be made for keeping it at least modestly efficient!
It's when the armature itself is a critical component -- like the bullet in a gun -- that flux density needs to go way up. Which is why railguns have been such a problem to develop, and why coilguns will never be more than a toy -- to replicate the pressure of a real (chemical propellant) gun requires 10s of T peak, and needless to say, some fuckoff big capacitors. (To be technical: a metric fuckload.)
Tim