insiders' issued shares EXPIRE; when they are issued they vest on a schedule and expire on a schedule so they Have to be sold or become worthless........ they don't get to keep them forever even if they wanted to. Insider's sales are planned in advance, meaning they select future sale date(s) and in so doing, have no real assurance or idea what the pps will be at the time of sale.
I have been issued shares by 3 co's in my career in such a manner and they all had expiry dates, blackout dates where they could not be sold (around Q's or other material events/announcements), etc...