arrated from ‘Abdullah ibn ‘Abbaas (may Allah be pleased with him), who said that he saw ‘Abd-Allah ibn al-Haarith praying, and his hair was braided and tied up at the back. He went and started to undo it. When he finished praying, he turned to Ibn ‘Abbaas and said: What do you have to do with my hair? He said: I heard the Messenger of Allah (blessings and peace of Allah be upon him) say: “The likeness of this one is that of a man who prays with his hands tied.”
Narrated by Muslim, no. 492
Al-Mannaawi (may Allah have mercy on him) said:
What is meant by “braided and tied up at the back” is that his hair was gathered together. “(The likeness of) one who prays with his hands tied” means: with his hands tied to his shoulders, which is not appropriate (i.e., it is makrooh), because if his hair was not loose it would not fall to the ground (when prostrating), so he would not be prostrating with all parts of his body, like the hands of the one whose hands are tied cannot touch the ground. Abu Shaamah said: This is to be understood as referring to when the hair is gathered to the back of the head after being braided, as women do.
Fayd al-Qadeer, 3/6
It says in al-Mawsoo‘ah al-Fiqhiyyah (26/109-110):
The fuqaha’ are unanimously agreed that it is makrooh to tie the hair when praying. What is meant by tying the hair is to fasten the braid of hair around the head, as women do, or to gather the hair and tie it at the back of the head. This is makrooh (not appropriate), but if a person prays like that, his prayer is still valid.
It doesnt seem to me they are talking about short hair