ITIL is at version 5 now - the idea of a process, is not exactly forgotten in the industry.
But you're working with a stochastic system. Even GPU matrix calculations are nondeterministic. It isn't possible, to the delete the entire source code and get exactly the same software back.
And any spec, that is specific and non-ambiguous enough to carefully construct the exact needs of each is... Well, that's code. Not a PBI, not an Epic. It's code.