I wouldn’t say every splash/drip/fade has ano flaws… it’s just more likely the anodizer will have a flaw on a multi-step anodization.
Solids are simpler… BUT flaws are much more obvious on a solid finish. If your setup is not surgically clean, you are likely to find flaws.
On one color acid washes, it’s impossible to see what is an ano flaw and what is part of the acid wash, so these finishes are the easiest to do.
In my experience, two color acid washes are next easiest. Followed by Splashes, then Fades. Multi layer finishes like fade-splash, hand painting and stencils are the hardest of all to complete flaw-free.