Premine can't be locked in certain block height since Dero switch to a BlockDAG structure.
Date of foundation and Team Reveal as far I know was delayed after Smart Contract Implementation.

In a Blockchain you can determine at which height you can lock the premine, because the consensus create only one block at time.
In a BlockDAG one or more blocks can be created a the same time, so you can't determine at which height to lock the premine.