It's not an exception to the lockup, they are sold as part of the IPO. It's like taking money off the table in a VC round. Broadly speaking shares can come from

It's not an exception to the lockup, they are sold as part of the IPO. It's like taking money off the table in a VC round. Broadly speaking shares can come from three places when they are sold: new, which causes dilution, allocated but not granted, which is where the majority of employee grants come from, and finally vested ownership that is held by individuals. An IPO will have some mix of the latter two almost always. The relative proportion signals how bullish the insiders are to future prospects for the stock.