Trailing newline handling in rectangular regions varies with rectangle-mark-mode

Rectangular editing in Emacs provides blockwise cut and paste independent of line boundaries as documented in the manual under Rectangular editing. When a rectangular region spans multiple lines, the handling of the trailing newline at the bottom edge is reported to depend on the rectangle-mark-mode setting. This variation affects how yanked text integrates with the kill ring and subsequent editing operations. The precise conditions under which the newline is preserved omitted or inserted remain ambiguous across different Emacs configurations and region shapes.

Under what rectangle-mark-mode values is the trailing newline consistently preserved during rectangular yank?

Does the kill-ring insertion order change when rectangular yank follows a non-rectangular cut, and if so, why?

Is the documented behavior intended to support multiple line counts, or is it an unresolved design ambiguity?