There's actually a couple of different "mil specs" even in just the USA.
Mil Spec 2000 is a document detailing the exact methods and procedures for electrical connections by technicians. So an Amiga (pre SMD, anyway, just the through hole versions) could be described as "Mil Spec" if all those solder points, cable joints etc actually met that specification. Which depends on the competency (or not) of the human being assembling the components.
Mil Spec semiconductors are rated at low to average speed (compared to scientific or civilian equivalents) but operate over a much bigger temperature range, typically some degrees sub zero up to 125 Centigrade. This means they have a better chance of working correctly under stressful and / or combat conditions. Operating close to zero is iffy because of condensation issues in equipment causing water formation causing short circuits.
There are Mil Spec standard numbers for equivalents to the commercial equivalents, and in some cases they can be overclocked more because they can be overvolted more.
Not always. Overclocking is not a guaranteed success on every processor, whether civilian or military.
So, as a claim, it is not as precise as "chipheads" like us might wish.
