Discussion on:

Ensure consultancy engineers know how to wire networks

Totaly agree with the statement. It is crutical you understand the cabling infrastructure as the name implies it is the the infrastructure / fabric which the network is built apon.

It is definetely a good idea to get a close relationship with a cabling / electrical company whom you can trust and who understand that structured network cabling is not just like electical cable.
I had a project to oversee the wiring of a new building. The electricians had cut and joined all the Cat5 cabling and did not test before enclosing the walls. I had walked through this with the electricians and explained there should be no breaks in the cables, however they ignored what I had explained and decided that it was just cable and they would run the same way they ran power cables. Needless to say most points had failed and we had to rip out walls and ceiling to rerun cable. Lessons learned, choose a contractor you know understands data cabling.

And for color blindness. Every keystone jack I've seen in the past five years (from any manufacturer) is color-coded. All the contractor needs to know is "Are we wiring 'A' or 'B'?"

At first I thought you said that the engineers had theoretical knowledge, but lacked hands-on know-how.
But then later, you say they should have more theoretical knowledge (in both senses).
I don't understand how that follows from the problem you described at first.

Would have expected more of a "let your techs play with wires during downtime" conclusion. Let them do it, hands-on, and they'll have something to pin their theoretic knowledge on; that'll make them much more dexterous with their work.