This is what i have come to understand about what the alkalinity proponents suggest:
The blood must maintain a near neutral pH.
The internal body should be more on the alkaline side. This includes the intracellular and extracellular fluids such as found in the organs. Excludes the blood.
The external body should have a slightly acidic pH. This includes the skin and the gut. The gut is the tube that connects the mouth and the anus. That tube is considered part of the external body since it is in contact with the outside world thru the food we ingest.
They being said, they tend to focus on the internal body pH with their recommendations. Probably because it is the more difficult to maintain with today's lifestyle and diet.
Plus, even if the blood is maintained at a near neutral pH, that does not mean that the buffering system is not taxed and stressed. Ideally they strive to reduce the large workload of these buffering system. One of the best ways to do that in their opinion is to increase mineral consumption and improve diet.