It's funny how one of the hardest touhou games had the easiest extra. Seems like ZUN was apologizing for making you go through hell and back just to unlock the extra stage.
Touhou 15 is hard, no two ways about it. I've played Junko enough times to carve a path through some of her cards and nonspells but a couple are just insanely hard, and Clownpiece is even worse. Hecatia's stage is absolute hell and while she has some spellcards that are ok in terms of difficulty, most are at least challenging and her nonspells are hell. Please, tell me what makes Touhou 15 so easy to you?
3 years late but it gives you a small amount of points, plus it's a reference to Space Invaders where the UFO would be worth more or fewer points depending on how many shots you'd fired before hitting it.
Nue was never the least difficult Extra Boss if you ask me. At the time of release, that title would have gone to Suwako. UFO's Extra Stage is brutal, and it's difficult to make it to Nue with more than 3 lives. These days, Okina and Saki make for the least difficult Extra Bosses, but "least difficult Touhou Extra Boss" is like saying "least destructive atomic bomb". Generally speaking, most Extra Stages are harder to clear than their respective game's Lunatic difficulty. Trying to beat an Extra Stage before you can get a Hard mode 1cc is ill advised, but you can always do what I did after just getting to the point where I could do Normal mode 1ccs, pick an Extra Stage and bash your head against it every day for 3 months. At the end of the day, it all comes down to practice, and the more fun you're able to have with these games, the more you'll want to play them and naturally improve, so don't set your goals on what looks the most achievable. Pick the game with your favorite music! The coolest looking attacks! Just go for it!