Change of behavior of "space" display property and face property

[Qiantan Hong]

Open an empty text file, M-: (insert #(" " 0 1 (face (:underline t) display 
(space :align-to right))))

On Emacs 28, this produce a blank line with underline.

On Emacs 29, this produce a blank line without underline. In general, “space” 
display 
seem to disregard any face property.

Is this intended or is this a bug? “space” display respecting face property is 
useful for
typesetting. For example. I use it to display a horizontal separator under my 
header line.

Best,
Qiantan