A friend claimed this and I can neither confirm nor refute it so far. Is this true?
It is true, yes. You can confirm this in the civilization wikia:
To have access to any Resources, especially Strategic and Luxury ones, you need them to be inside your territory. Founding cities near them (1 to 3 tiles away) is the best way to assure that. Never forget that a city may only work tiles that are at most 3 tiles away from its main city tile. So, when choosing the spot, try to include as many Resources within 3 tiles of it as you can. Even though your budding city won't include them into its territory yet, it will start growing it later with exactly this in mind.