Honestly, I'd take that with a pinch of salt.
I was told by midwives during both pregnancies that I looked like I'd go early.. DS was 40+5
DD was 41+6
And to be honest, there's a million signs but the only real sign you can pay heed to is water breaking or contractions. My plug went a week before I laboured, both times. The signs are really only a 'maybe possibly if you're lucky' type thing not a definite.