It is pretty traditional for owners to credit the architect, even well after then own the course.
There are a couple of issues in play as to Frank's original question. It seems that Von Hagge's company had at least a sub-contract to assist in the design of the course, so they should be credited. I had a few of these, one with Jay Morrish, another with Gary Baird, and of course, many where tour pros were under contract as consultants. Of course, all parties are credited without much regard to exactly what % of the design they may have done. I think the theory is, they are all subject to the same lawsuit when things go wrong. I haven't heard of a case where the jury award was split along the % each party participated in time or effort.
This is a different kettle of fish than the question of an associate working for a firm under contract to design a course. In those cases, the tradition, if any, is to allow the head of the firm to dish out credit as they see fit, from none to the principal and primary associates who played a substantial role. It is highly unusual to list more than one associate on any project, and most firm heads, even if only figureheads at that point in their career, decline to list anyone.
And, in many cases, several associates do work together, and getting the project out the door with full plans, etc. does take a lot of work. Many (I think Mike Y and I agree on this, but he can chime in) associates take sketches from the main guy, do a lot of detail work, but the head of firm still believes he should get all the credit, if for no other reason he/she has put the infrastructure in place to get jobs done (office, staff, software, etc) and as per above, is the one who will get sued, so you really don't know if an associate can do that when on his own. Being a talented designer and being able to get a project to the finish line are often two separate skills. The former is not worth much unless you have the latter as well.
The real test, to me, would be to ask the clients daily on site representative who they called when they had a problem? Usually, an architect designates one associate to do that when they can't be present to answer the phone, make a site visit, etc. If the client usually talks to the head of firm, perhaps no one else should get much credit. If they were comfortable taking to the lead associate architect, then maybe they should.
While its the architect's prerogative, nothing stops the client from answering questions honestly, and many when asked will say "such and such did most of the work" and then its out there, and it tends to stick. That can cause some problems when an associate leaves and takes a wee bit more credit for a project than the head of firm recalls!
OT, but similar things happen on the contracting side. You run across ten guys who say "I built that project for Jack" (or whoever) and it takes some digging to find out. I have people say that as shapers, and even down to lowly guys who run the seeding tractor, but want a piece of the golf contractor market, so they fudge a bit.