Chukar's own account

The "let go of the stick" part is probably a souvenir of the period (some 50 years ago) when gliders had airbrakes that kept the speed below Vne even in a vertical dive (this used to be specified in the standard class rules, before the Libelle/Cirrus/ASW-15 generation came up - see the Schweizer stories about vertical dive test flights). The technique you found in many gliding (teaching) manuals was indeed: "trim fully forward, airbrakes fully open, let go of the stick and rudder". At least here in Europe.

With modern gliders, the Vne limit will be reached long before a vertical dive position even with airbrakes fully deployed (I seem to remember that a 30° dive is sufficient with some open class self launchers or fully ballasted gliders). So it is probably common sense to try to hold the stick steady in pitch after trimming forward.