On a phone
Reading view drops the canvas for a plain column.
The canvas is built for a pointer — dragging, marqueeing, drawing yarn. On a phone that is the wrong instrument, so Reading view renders the same workspace as a column you can actually read.
Frames become sections carrying their members, then loose items follow in the order you placed them. Connections are spelled out in words — "supports X", "refuted by Y", with your reasoning underneath — because the drawing is exactly what a small screen cannot give you.
Phones get it by default. It is a toggle, not a lock: switch back to the canvas any time, and nothing about the board differs between the two.