Clarification: Specifically in a permanent bathroom we are worried that perhaps he will do his needs there, but in a temporary one, where one does not tend to do so, one is permitted to urinate there.

Clarification (cont.): And we are not worried that he may do his needs there.

Implied Question: And that what we learned later on that 'One may not urinate even in a temporary bathroom ...

Answer: that speaks where he is holding his Tefilin in his hand, where we are afraid that he might wipe away the drops that fall on his legs, or come to touch his Amah.

Clarification: This can only be due to the space ...

Proof: because if there was no space at all, then they would not save, since it would be similar to food that one mixed with cement, that are subject to Tum'ah in the tent of a deceased person.

Rejected Explanation: The Gemara does not want to answer that 'The things that I permitted to you' - in a temporary bathroom, 'I forbade to you' - in a permanent one; meaning that Gedolim are forbidden whilst wearing Tefilin on one's head, whereas to urinate is permitted.

Reason: Because we do find such a distinction in a Beraisa.

Conclusion: Whereas the distinction between a Tefach and two Tefachim (which the Gemara finally cites) we find specifically mentioned in a Beraisa (ha'Rav Rav Yosef).