A 60% keyboard is the one in every desk photograph: a clean rectangle, no function row, no navigation cluster, no arrows. It looks resolved because things have been removed.
Then you edit a sentence.
The layer tax
On a 60% board, the arrow keys live under a function layer — hold a modifier, and four letters temporarily become arrows. This works. It also means every small navigation move costs a two-hand gesture, and the cost is paid hundreds of times a day by anyone who writes rather than types.
Sixty-five per cent adds one column on the right: arrows, and usually Delete, Page Up and Page Down stacked above them. The board grows by about twenty millimetres. The layer disappears.
What you still give up
The function row, which matters if you live in a piece of software that uses F-keys as verbs, and the number pad, which matters if you live in a spreadsheet. Both are honest losses. Both have a separate answer — a numpad block that comes out of a drawer costs less than the desk space a full-size board takes every day of the year.