Conflicting Writer Advice

I’m curious about why successful writers sometimes condemn the practices of other equally successful writers when giving advice to starving writers. It’s not like they’re saying, “This is what worked for me….” Often a successful writer will say something along the lines of “Do A, but don’t do B.” Meanwhile, another writer, who is every bit as successful as the first writer, will say “Do B, but don’t do A.”

What I wonder is, are these writers aware that they are giving conflicting advice? Are they aware that other writers have reached success by doing the exact opposite? I don’t think these writers are in some kind of argument with each other, I think they just don’t know what they’re saying. It would make more sense if they gave their advice in a “this is how I did it” manner, instead of “You must do this and you must not do that.”