You can influence results, but you can't outright fix them. If a scrub makes 3 after 3 you can't stop that. But you can make things easier by calling timely fouls or not, and having key players in foul trouble. You can try to extend series but if one team is so much superior than the other (see 14 Heat/Spurs) even the refs can't change that (eg. heat went on a run to start game 5 with some friendly whistle but Spurs clawed back because they're so much better).
The league isnt stupid enough to say anything incriminating on text/email/paper etc. As Donaghy pointed out, when the league wants a desired result they infer things like "you're missing a lot of guys hacking at player X" etc. Once you point out enough examples, the refs get the picture. Its like why do teams down 20 pts get friendly whistles? Because its better for ratings when the games are close (but not so close as to put the desired winning team's lead in jeopardy).
Also Lebron coming back 3-1 (something no Finals team has done) and ending CLE's sports drought is an even better storyline than GSW going b2b. But most importantly, the league got its wish with a game 7 (which as it turns out is the highest rated NBA game since game 6 of the 1998 NBA Finals where Jordan hit the shot over Utah).