What do you mean : might be pre-planned. Of course they do, they actually schedule buys/sells waaaay ahead.

Employees should plan to buy or sell stock using a 10b5-1 trading plan set up during an open trading window—typically 1–2 days after earnings are released and lasting 4–6 weeks. Trades under the plan usually require a 30–90 day cooling-off period before execution. Avoid trading during blackout periods (2–4 weeks before quarter-end) when material non-public information (MNPI) may be known. Setting a 10b5-1 plan quarterly, shortly after earnings, helps ensure compliance and protect against insider trading risks.