Grenville
After an total power failure assuming no pilot action and forward flight the rotor speed will decrease. This will have greatest effect on the advancing blade (think standard lift formula). This will result in the front of the disc flapping down (flap forward - effect 90 degs onwards). The aircraft will therefore pitch nose down. In the hover there is no difference in lift across the disc so the dominant effect would probably be a reduction in downwash on the horizontal stabiliser so again nose pitch down. This may also contribute in fwd flight.
A lot of other stuff happening will mask this however like the yaw.
And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)
And for interest my opinion is that a one size fits all is stupid for entering autorotation. Entry should be tailored to the circumstances. There are some basics to get you started (fly the aircraft, maintain NR, make a plan and follow it, get the gear down if appropriate, say something funny for the CVR) but slavishly following advice in the face of different circumstances could get you killed. AVIATE!