I’ve been frustrated by forgetting to use these tiles as well, but BGA implements this correctly. The siesta roof markers can only be used during the Farm Phase or the Revenue Phase, as indicated by the blue/green background. Choosing a Donkey Marker is the first step of the Transportation phase. This distinction ensures that all players have access to the same information when choosing a donkey marker.
One could argue for other anytime effects during this step, such as the roof marker that makes a delivery, but simultaneous selection is not uniquely “your turn”, which is when rules state you can take an anytime action.