I bet millions of cats are named with names like "Sam". Are they less well trained? I bet no (But I have no proof either).
Let us focus on the reason Chris C. Pinney gives you for his suggestion:
This will allow it to differentiate between its name and those one syllable commands you may choose to teach it.
What is a name?
As a human, we identify with our name. We do not only say: "I am called Anna", or "My name is Anna", but we also say: "I am Anna". Our names are an identifier for our whole personality.
For pets this is not the same. They don't identify themselves by using a name. But they can learn that when someone calls a special command (their "name"), it is good to give this person their attention. They know that they may get some treats or stroke if they come to this person when they hear that command. They can even differentiate between different names. E.g. if you have two cats named "Kitty" and "Chloe", Kitty knows that "Kitty" is her special command, but she does not have to react when Chloe is called.
To teach a pet a name it is necessary to always be consistent. If it is important for the owner that the pet knows its name, it is good to train it like any other command (e.g. give the pet a treat if it gives you attention after calling its name). If there are more than one pet it is important that always only the pet is rewarded which was meant and not the others, too.
The biggest problem with names and commands which can confuse pets is the repitition of commands without being strict. E.g. when you always say: "Stop Max, don't scratch...", "Stop Max, don't eat...", "Stop Max, don't jump..." after a while Max will think that his name is "Stop Max" even if you trained him before to stop when you give the command "Stop." And you can't prevent this confusion by using a name with more syllables or ending with a vowel. Because the cat does not care it it is named "No Max" or "No Maxi".
Because names are like commands for pets, I would suggest that it does not matter, how many syllables a name has and if it ends with a vowel or not.