First of all the matter in fact looks differently, when one reads both ahadith in Arabic.
As in imam Muslim's version it is stated:
In the following I'll be translating from Arabic language, as these translations are of my own take them carefully!
... عَنْ عُبَيْدِ اللَّهِ بْنِ مِقْسَمٍ، أَنَّهُ نَظَرَ إِلَى عَبْدِ اللَّهِ بْنِ عُمَرَ ...
I think the second one should also use the pronoun He referring to Allah. If you look at the Arabic, it says
وَقَبَضَ يَدَهُ فَجَعَلَ يَقْبِضُهَا وَيَبْسُطُهَا - ثُمَّ يَقُولُ أَنَا الْجَبَّارُ أَنَا الْمَلِكُ
Allah is الجبار and الملك. So it must be Allah saying that, and therefore the words before must be referring to Allah.
Allah knows best.