Some of the bigger B&S engines have decompressors, which relieve the compression for starting but stop operating as soon as the engine gets up to idle speed, but Ezyspin is not like that. It holds the valve slightly open during the compression stroke regardless of whether the engine is starting or running at maximum speed. B&S say they can do this because when the engine is running faster than a few hundred RPM, not enough gas has time to leak through the slightly open valve to have much effect on anything. Of course the valve is fully closed for the expansion stroke. The idea seems a bit weird but B&S is the world's largest manufacturer of small engines AFAIK: they must know something about what they are doing. It is not all that different from the "half compression" feature that some very old cars had, to make it possible to start them with a crank handle - but you disabled the half compression as soon as the engine started, unlike the B&S version which operates all the time.
I haven't worked on a Honda engine and I don't personally know whether it has a feature similar to Ezyspin, or just uses a conventional centrifugal decompressor. Someone on this forum will know the answer. Whether your engine has a decompressor or Ezyspin, the feature will operate while starting - so you would get the result you have described when you pull it over by hand and watch the valves. Since your engine works properly once started, whatever feature it uses for reducing compression while starting seems to be working.
The chances of Honda (a very reputable engine manufacturer) having made a complete shambles of making a camshaft, years ago before they moved mower engine production to China, are fairly low. I think it is more likely that the camshaft is not the cause of your problem. Nevertheless it is theoretically possible on a worn camshaft for the base circle to erode, while part of the lobe is still present (though perhaps horribly deformed). Such things are not usually worth investigating though, until you have eliminated all of the more common problems.
Post-Edit: This engine, like all of the small OHV Hondas, has a decompressor to make it easier to pull the pull start. The decompressor bumps the exhaust valve open during part of the compression stroke. It is deactivated by a centrifugal device mounted on the camshaft timing gear, at any engine speed above about 600 rpm.
matts156 described the decompressor's operation accurately in his post #17633, above in this thread.
Last edited by grumpy; 14/10/13 05:05 PM. Reason: Add post-edit
