pic/-ms inconsistency in groff 1.23.0

[Douglas McIlroy]

Upon updating from 1.22.4 to 1.23.0 this pic delimiter
     .PS 6i
failed; it worked in 1.22.4. The updated pic turns it into
     .PS 6.000i 6.000i 6i
which causes groff -ms to barf:
     s.tmac: ... error: .PS: expected 2 arguments, got 3; not
preprocessed with pic?

groff, pic, and tmac.s were all updated. I can find no dregs from
1.22.4 on my computer.

A third party had their fingers on the code: cygwin. Is this
inconsistency their fault, is it inherent in 1.23.0, or is it
something more mysterious?

Doug