Company says If I resign during PIP , it will count as termination , no exit letter only termination letter , legal ?

So got pipd , got 2 months left , HR says if i resign during resignation it will count as termination , wtf , is this legal ? They are saying they will not give me a exit letter but give me termination if i resign How this legal ? What can I do ? #tech #advice #help #pip #snap #meta #linkedin #square #referral #help