The problem isn't that nobody understands what it means, it's that what umbarsc is arguing, "these Pokemon make UU feel like standard," means absolutely nothing. All arguments based on simple opinion have no bearing in the current tiering structure, and to say otherwise demonstrates either that you don't know what the current tiering structure is, or that you don't think that the current tiering structure is the right way to go, and that you think there's something fundamentally wrong with it. Of course, neither of these matter. The current tier structure is in place because it works, and it creates a playing environment where it is easy to figure out where the trends are going, as well as what the more powerful and influential Pokemon are.
That said, my standing on the whole NFEs in UU thing is that there are a number of criteria that set an NFE apart from its evolutions. I'll provide examples for each of the criteria.
1: Specialized Items. This is already well-defined and accepted in UU, but I figure it deserves mentioning anyway, as it falls within the bounds of acceptable NFEs in UU. Pokemon that get a boosting item that applies to it but not to its evolutions should be allowed in UU in order to utilize said item. Currently, this applies only to Clamperl (DeepSeaTooth and DeepSeaScale) and Pikachu (Light Ball), but it applies nonetheless.
2: Different Typing. This is already in play with Trapinch being allowed in UU due to being mono ground (and other things which need not be mentioned here). Pokemon with different typings have completely different sets of resistances and weaknesses, and thus, play differently than their OU counterparts. They also get different STABs, and thus may choose different moves for that reason. Scyther is an example of one that through typing fundamentally differs from its fully evolved counterpart. This could also apply to Shelgon, Seadra, Pupitar, and a couple other not really notable Pokemon (Magikarp lol).
3: Stat Spread. I really hate the whole "slower pokes can have an advantage in Trick Room" bullshit argument. So the idea would be that NFE Pokemon whose stat spreads differ heavily from the stat spreads of their fully evolved cousins can be considered different from their OU counterparts. Shelgon is a huge example of this. While Salamence has excellent attack, speed, and special attack as well as considerable bulk, Shelgon is more of a physical tank than Salamence with high physical attack and defense combined with low special defense and speed. Similarly, while Kingdra has equal offenses and defenses, Seadra has much lower HP, Attack, and Special Defense, making a special attacking set much more common (and a mixed or physical set much less common) than with Kingdra, its fully evolved counterpart.
4: Different Ability. This is the one that I think is the least important of the criteria. Some Pokemon have a completely different ability from their fully evolved form, which makes them play in a significantly different manner than said OU. This is most notable in the case of Pupitar, which carries Shed Skin instead of Sand Stream. Instead of being used as a tank to set up Sand Stream, it gets used as an offensive Pokemon that can be used to absorb status and heal it away with its ability.
These are the Pokemon that I think would see use in UU under these new rules:
Shelgon: Excellent defense with mediocre HP, but above-average attack. Its low speed might hamper it, but its high defense and useful resistances can allow it to come in and achieve a Dragon Dance and sweep. It has no real support movepool, and doesn't get reliable healing, so its tanking is pretty minimal.
Seadra: There are a number of ways that Seadra can fall. While it has a mediocre Attack stat, it does get Dragon Dance to boost it and its speed, making a physical set viable. It also has a good spread of attacks to hit with on the special side. Or it can combine the two and run something like Dragon Dance/Waterfall/Dragon Pulse/Surf or something of the like.
Pupitar: Rock-Ground has always been a great attacking combination, and few viable UU pokemon get STAB on both. Pupitar gets STAB Earthquake and Stone Edge with which to wreck face, as well as a number of other useful attacks. It can use Dragon Dance to boost its sweeping stats. It can use Curse to bulk up its defenses while using ShedRest to get a chance at an early wakeup. Shed Skin is an excellent ability that allows it to act as an impromptu sleep absorber as well as recover from a Burn inflicted on it by something like Rotom.
Feel free to provide feedback. I think this needs to get resolved ASAP so we can move on to more important stuff in the metagame.