Tirmidhi

Hadith Commentary:
By "round," it is not meant that it was completely round, but rather that there was roundness to it.
In Arab culture, this is considered a part of beauty. Along with this, the cheeks of the Prophet (sallallahu alayhi wa sallam) were not puffed, but rather smooth, as is mentioned in another narration.
His beard was rounded and thick, almost covering his chest. His hair was very black, his eyes were naturally lined with kohl, and there was a reddish tinge in them.
In short, he (sallallahu alayhi wa sallam) was the embodiment of beauty.

Hadith Commentary:
According to the narration of al-Bara’ ibn ‘Azib radi Allahu anhu, the face of the Prophet was radiant and round like the full moon (the fourteenth night’s moon). And according to Jabir ibn Samurah radi Allahu anhu, his face was luminous and shining like the moon and the sun, and somewhat round.
(Sahih Muslim, al-Fada’il, Hadith: 6084(2344))
Rabee‘ bint Mu‘awwidh radi Allahu anha states that the face of the Messenger of Allah sallallahu alayhi wa sallam appeared as if the sun was rising.
(Sunan al-Darimi: 31/1)
‘A’ishah radi Allahu anha narrates that the noble face of the Messenger of Allah sallallahu alayhi wa sallam was full of light and extremely beautiful.
Whenever anyone described the radiance of his face, they would liken it to the full moon, meaning that people would see his beautiful countenance shining like the radiant moon.
(Dala’il al-Nubuwwah: 298/1)
The meaning of these narrations is that his face was not elongated like a sword, but rather round like the moon.
The moon possesses both roundness and radiance.
Therefore, likening his face to the moon is superior to likening it to a sword.