I don't think that's true at all... A clone is a clone - it is the exact genetic duplicate. Even after years DNA doesn't change... it is the same plant, though in a different form than the seed mother. I'll try to give you some better answers:
1. You don't really need a mother plant, but it is nice to have one. With a mother you can take clones every two weeks (and therefore have plants starting veg every 2 weeks) if you wanted to, and you don't have to worry about damaging your crop's eventual yield by cloning from them. You can also top your plants, and clone the tops, on top of having a mother plant, for max efficiency.
2. Yes, cutting the ends of long-leafed clones results in the plant focusing root growth... But you're doing more than that: you're decreasing the amount of energy taken in by the plant. Without a root system of decent size, a cutting can't actually take in and utilize all the light it receives, which is why low light levels and fluoros work well for cloning. The cutting itself, unrooted, also can't take up water, so it's important that it stays moist with nutrient-free water, with a humidity level of 80-100%. I use a humidifier aimed right at em, once they start rooting, and a dome before that, with plenty of water inside the cloning chamber to maintain 90-100% humidity. Most important two things about cloning are humidity and constant light (only direct light if using fluoros... wouldn't want to expose clones to HPS unless it is a safe 3 feet away).
