Of course it’s possible. I don’t think anyone has found a way to cheat themselves a couple thousand of paragon points by finding some sort of exploit / vulnerability in the game, or the client-server communication protocol. A couple of notes however:
- The current paragon system, known as Paragon 2.0, was introduced around early-mid 2014. Pretty much 7 years ago. Before that, there was 100 PL cap per character, and paragon points weren’t shared between chars (according to wiki, I haven’t played it back then);
- The paragon acquisition rate was not always the same over these years. AFAIR Blizzard has made several changes after that. It wasn’t always the same curve as it is now;
- Greater Rifts were introduced in 2.1, which went live late August 2014. Moreover, they were capped at GR100, although back then GR 35 was considered a decent solo clear. If that’s not enough, wiki states that first groups that reached GR100 were only able to do so in 2.5, and that’s early 2016.
I’d say, getting to 17k should have taken considerably more than 40 hours a week, on average.