I dunno. It's a bit hard to tell from his post how senior of a "manager" they want to make him. A first level manager could easily only have 10 years of experience, so if he's a 20-year veteran on the technical ladder he could be making more in that role than the first level manager range typically is. And many companies DO have a specific range for a specific title (which doesn't mean exceptions shouldn't be possible).
It could be reasonable to pay the same for a top end engineer and a low end manager. And they could be right that with his technical chops, he could advance quickly through the management ranks if he has a talent for it. And if not, then he's got a year or two of management on his resume at the same pay with an excellent technical background. That should make it easy to get another management job, at a higher rate if warranted.
That said, it does sound like they want him to manage quite a few people. So not such a simple job. And I'd like to know if it is what most of us probably think of as a manager, dealing with budgets and senior management and a lot of other things or if they want him to be a supervisor...scheduling shifts and assigning tasks primarily.