If a Mystic focusing on Giant Growth changes their reach, does it provoke opportunity attacks?
You can make an opportunity attack when a hostile creature that you can see moves out of your reach.
A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else's.
This implies that you can make opportunity attacks on your turn.
For the UA Mystic (V3) class, the discipline Giant Growth states:
While focused on this discipline, your reach increases by 5 feet.
And the class feature Psychic Focus says:
You can focus psionic energy on one of your psionic disciplines to draw ongoing benefits from it. As a bonus action, you can choose one of your psionic disciplines to gain its psychic focus benefit, which is detailed in that discipline's description. The benefit lasts until you are incapacitated or until you use another bonus action to choose a different focus benefit.
My understanding of this is that, assuming I am focusing on Giant Growth and have a reach of 10', if I use my bonus action to focus on something else, my reach reduces to 5' and all creatures that are further than 5' away from me and less than 10' provoke opportunity attacks. Is there any reason that this would not be the case?