Can you definitely unlock the modifiers before the first boss, or is that a possible bug?

Many people have said that they unlocked the modifiers after maxing out the skill tree and then dying to Prophet a few times, but I've seen several posts from people saying they can't get it to happen.

I suck at these games but I still want to play, so I'm waiting to see if it's guaranteed that you can unlock the modifiers early before I spend the $70. (I know, get good etc)