This! So very much this. Method 1 is easy enough, but wild RNG (in RSE AND FRLG) can just die in a fire. I've had to reRNG spreads so often just to get certain Pokemon with the right IVs. Hell, I had a beautiful Adamant spread that worked for like 10 encounter slots (which is HUGE!) and for a total of maybe 25ish opportunities to generate a 5iv spread, but it would always fail when going for surfing of fishing encounters and it would usually switch from H-2 to H-4 somewhere around the middle of streak (if that makes any sense). What's more, I was missing Adamant Horsea and Wailmer (fishing encounters) so I went to Sapphire and RNG'd them there. And lo and behold, H-2 AND H-1 both failed, so I had to RNG Sapphire a third time to get a spread that generated these two (it doesn't help that RuSa have less encounter slot options to begin with because of the lack of Synchronize).
So yeah, trying twice is definitely not enough. But as Skymin said, even that doesn't even mean anything. I've had to redo the Naive hex flawless twice (different frames) to find the Pokemon I was looking for with the correct stats. :/
RNGing in gen 5 is easy. RNGing in gen 4 is easy for most cases (except maybe PokéRadar, but that's more trial and error and just teh maths than anything else). RNGing in gen 3 is NOT easy.