With Measure Type by Glyph Bounds on, point type is measured by its
glyph outlines and its underline and strikethrough bars, as the canvas
draws them. A typed W or H gives what is drawn that size, and underlined
or struck-through spaces are measured by their bars instead of the em
box.
The texts now say that each point type object selected as an object
(not inside a selected group) is measured this way, that moved type
snaps by its ink box, and which Arrange Tools commands follow the
option: Swap Objects, Replace with Top Object, Set Size of Each and
Sort Objects. Arrange in Grid and Group Overlapping Objects keep
measuring visual bounds.