If anything, this adapter will add back in the inductance you would otherwise lose when going from a DIP to an SOIC. I've used similar things a lot and never had any trouble. Do remember though, that the pins on the adapter are header size pins, and not as narrow as the legs of DIP chips. It will probably fit the size of through holes on a PCB you'd usually leave for DIP chip legs, as you usually leave relatively big holes, but it will not fit in to a DIP carrier socket, and won't fit a PCB if the DIP chip's through holes were made as narrow as they can possibly be for DIP legs.
"Milspec" is about surviving being treated roughly in rotten environments, so long as the PCB itself is securely held inside a toughened case and the electrical inputs/outputs entering/leaving that case have appropriate protection from ESD or being connected to the wrong voltage which just happens to have a similar style of lead to the one the user is supposed to connect, then I'd say just about any circuit can probably be "milspec". Whether DIP or SOIC or SOIC on DIP adapter would make no difference here.