There are three type of photographers that do endorsements.
1. The most visible are the ones that look for endorsements first, then try or use the project depending on what the endorsements pay. That's there main business model and if it works for them then that's the purpose of a free market.
2. The next are photographers that actually have used the equipment, but will only use it full time if for paid endorsements and or given or loaned the equipment for further long term use.
3. The last and probably most informative are the photographers that buy and use the equipment first and then are asked to do endorsements based on their work with the equipment.
Without knowing all the specifics Frank seems to fall into the last group, which is much easier to take and more valid to believe.
Now whether anyone believes endorsements or not is their business and like any high priced item everyone should try before they buy, or at least do some serious research before they buy.
It doesn't move me an inch if someone endorses something or not. I base all my buying decisions on my use, sometimes I'm right, sometimes I have to make changes, but that's the way of life.
When I bought my Red cameras I never cared if Peter Jackson used them. I needed a deep raw file for multi cam projects and RED was the only option.
When I bought my Nikons there were not a reflection on my Canons as I use the cameras in different projects, same for my phase backs, same for my contax, same for my next camera purchase, whether that be an H5d or a Canon 1dx.
They are all very different devices that do very different things and though I might someday buy a D800 (at least I will eventually test one next year if my schedule permits), I doubt seriously if I will use them to replace my current cameras.
Bottom line is I know about 20 good photographers and none of them use exactly the same equipment combinations including cameras, lenses, lights, supports etc.
They use what works for them, they use what works for the project, but most of them test first, buy second.
Second bottom line is to find a good dealer. Sure you can shop around and sometimes save what looks like substantial money, but in the long term, you'll nearly always pay more, because when any issue arrives you're on your on.
Also working without a dealer really doesn't build relationships or equity. Personal equity is the key to successful business, whether your the client or the supplier.
I'll summarize this by saying that if you work a number of years, you'll always have some issues with equipment and/or suppliers. It happens and there are two ways to deal with it.
Find a positive solution and move forward, or stay in the past and continue to diss a brand or product which really doesn't make anyone any money or move anyone's work forward.
Never discount positive equity.
Everyone shoots and works differently but freezing motion can come in a lot of ways.
This image was frozen at 1/90th of a second with a Cotnax and Phase back, by just tracking with the subject.
This image was purposely shot at slower shutter speed to accentuate speed.
There are more than one way to work.