When using Spreading and Dreadful Mire, does it matter if you don't have a Sacred Site in the origin land when you resolve the first threshold (e.g., because you targeted via Entwined Power)?

When using Spreading and Dreadful Mire, does it matter if you don't have a Sacred Site in the origin land when you resolve the first threshold (e.g., because you targeted via Entwined Power)?

No, "the origin sacred site" is just land you picked as the origin back when targeting the Power. There isn't a second check for if that land is still your sacred site.
This only matters if you still have Presence in that land (e.g., because you and the Spirit you're entwined with each had exactly 1 Presence there); if none of the Presence there is yours, there is no Presence you can move.