[Taniwha]

Yes it's a primitive form of gate array.

The thing is gate arrays are sort of something between a full custom part and an FPGA, they cost less per chip than a gate array, but more per chip than full custom. On the other hand NRE (up front 1 time cost)) is a lot lower than for full custom (I've built both).

These parts are mil-spec which means that their volumes will be lower, it may have made sense to build a mil-spec pad ring then spin out a range of low volume mil-spec 7400 parts from it