the u.2 form factor indeed evolved from chassis designs that were originally 2.5" drives. It's now kind of becoming obsolete with new designs using things like E1S, E1L (exactly the correct height to be slotted into a 1U server, it's like a slightly wider M.2, but meant to be insertable and removable), and E3S and E3L.

Note that the 245TB is an E3L, the half size version of it come in smaller size.

https://americas.kioxia.com/en-ca/business/ssd/solution/edsf...

https://www.exxactcorp.com/blog/storage/edsff-e1s-e1l-e3s-e3...

https://www.simms.co.uk/tech-talk/e1s-e1l-the-new-server-for...