One can only eat until the time of Biur of the very first type
Because even the last type contains a forbidden taste of the first type.
One may eat until the time of Biur for the last type has come
Because even the first contains permitted taste from the last type.
One may eat each type until the time of Biur for that type.
Because taste doesn’t matter in this context.
These explanations are from the Meiri. It is not clear why having permitted taste would permit other types according to Rabi Yehoshua, nor why taste wouldn’t matter in this context.