From a Reddit comment last week:
Clarification here, CVS cut the retail price of the existing generic for Adrenaclick (known as Epinephrine).
This generic has been around for a while, but isn't an A/B rated generic so it's illegal for a pharmacy to dispense this if a prescription is written for EpiPen. We can dispense this if a prescription is written for Adrenaclick or Epinephrine.
Make sure your doctor writes a script for Adrenaclick or it is illegal for us to dispense this cheaper generic to you
Edit: The injection device of each product is what limits the A/B rating. Adrenaclick and EpiPen have different autoinjector systems. Yes the regulations are that strict. Here's a video showing the difference between Adrenaclick, Epipen, and AuviQ (which has been recalled and discontinued).