Pgps -mm macro does not work

Binary package hint: groff

man groff_mm says:

" Pgps Controls whether header and footer pointsize should follow the
              current setting or just change when the header and footer is
              defined.
              ValueDescription
              0 Pointsize will only change to the current setting when .PH,
                   .PF, .OH, .EH, .OF or .OE is executed.
              1 Pointsize will change after every .S. This is the default."

However, .Pgps 0 does not seem to have any effect.

I will attach a demo file, which begins as follows:

.S 5
.Pgps 0
.PF "''This should be in 5-point text''"
.P
This is 5-point text.
.S 12
.P
xxx xxxxxx x x x x xxxxxxxxxxxxxx xxxxxxxxxxx xx xxxxxxxxxxxx xxx xx xxxxx
(more text...)

The footer appears in 12-point, but should be in 5-point.