JaiJay,
'Necessary'? No. But good practice is probably a yes. Unless you can have another way/ways to reference procedures?
I'm thinking of it from a 'dumb reader' point of view - if there's no reference to (presumably more detailed) procedures in/on/from a process map, then how does anyone actually know that said procedures exist, let alone what to go looking for? Now, if there's a good system of induction/training in place (for example) so that everyone does know that, then that might be an argument for not having them.
But having said, that, you always have to play off the 'maintainability' of that against the case for having readers able to find and access the information they need, ie, the procedures.
If you are doing the rewrite now, and don't have all the procedures clear at this point, then it would be a major effort & night mare to try & keep it all straight. In which case, I'd go for 'v2' which doesn't have them, and then work towards including references in v3 when you are clearer. I hope that makes sense.
PS, sorry to hear about the previous history. Someone who provides that kind of garbage is definitely not worthy of the term consultant.