Seagate stopped making 7200 rpm 2.5" HDDs in 2013 [1]. I assume Microsoft didn't want to pay more for a 7200 rpm 2.5" WD Black HDD so that leaves 5400 rpm drives as the only option.

The hard drive in the Xbox One is a 2.5" 9.5mm Samsung Spinpoint M8 drive [2]. Seagate purchased Samsung's HDD business in 2011 [3].

[1] https://techreport.com/news/24439/seagate-to-stop-making-720...

[2] https://www.reddit.com/r/xboxone/comments/1r5gc6/xbox_one_us...

[3] https://www.seagate.com/gb/en/news/news-archive/seagate-comp...