Yes, the clarification of muscular endurance relative to physical stamina is accurate. Muscular endurance infers that you maintain a level of 'quality' performance while physical stamina refers to your ability to continue performing in the face of fatique. This is the reason your cardiovascular 'aerobic' training can also be of great benefit to your stamina. If you can cover the distance of a golf course with some uninterrupted, measured degree of intensity, you will raise your aerobic threshhold and walking the course (even with the addition of heat and humidity so prevalent in the season) will be less taxing. If you can run that distance your golf walk will be almost uneventful in terms of overall stamina. This usually means your posture is better allowing you to bring the same physique to each shot. I recommend trying to get some cardiovascular work (walking, biking, running) outside to better acclamate yourself to the environmental factors on the golf course. One of my golfers has done his heart healthy work on his treadmill every day for the last few years. Early this spring he started going outside for his work and says he already has seen improvement in his stamina in his golf game on a couple of our hotter days. He is going on his annual trip to Palm Springs next week, I'll let you know if he fares.
I think I need to clarify a little, too. I see general training for body health and training for your sport as two complimentary and seperate workouts. It doesn't mean they each take an hour. When I am playing tennis I shorten my general workouts by ten to fifteen minutes and do a few minutes or sport specific movements/exercises. Think of the football player. He trains in the gym and then he does his drills on the field. Each individual player trains at the level of their needed performance and their body type. It's no different in golf than any other sport.
Finding a balance between your play and your training protocols (cardio, fitness, sport specific neuro-linguistic training;yea I know it's usually mind stuff but isn't TGM until you feel it?) training is the key but consistency is the secret.