Who's to say the Emperor only had one astral tadpole? It's not unreasonable that he may have been secreting a spare or two.
Often it seems like some people would prefer to find flaws. Absence of knowledge presents as certainty.
It doesn't matter how many he has, the emperor will only offer one. And you can get him to leave without giving you any. Easiest is by attacking him, he just teleports out with no dialogue.
If you have Gale in the party, Orpheus entire dialogue is written around whether you have obtained the tadpole or not. That is why so many people have had problems in convincing Orpheus not to turn anyone into a mind flayer.
