a-That neck you are working on, "California Series". Is that one of the American made Squiers? Looks kind of rare!
That "Squier" is a chinese one

the neck have a gross mistake construction. Necks with fingerboard shouldn't have the canal for the rod in the back, those have...
b-So if I'm understanding it right, the purpose of the bias was that you had extreme backward bow and you forced it into a extreme forward bow in the opposite direction to correct the problem and did the bias work successfully??
99% of the time it does work alright !
In the pics you see three different instruments, actually 2 china Squiers, the 1st in my 1st post, it just needed a neck adjust;
then a Yamaha bass, with an abused neck and cracked head stock. It did adjust about 98%, playable thou.
And then the one with loosen fingerboard. Bad glue work, it was loosing slowly.
The method is always about the same, but, Each neck is different, need different approach, the pressure is applied in different spot in each case, more or less pressure, it is always easier to work a back bow, the strings does the work, sometime the use of a shim between the strings and the fingerboard is necessary to get enough amount of pressure.
Back bow or forward bow?! English isn't my mother language and I do not know sometimes the correct meaning of some expressions(sometimes english is backwards for me).
So just to clarify, for me back bow is when there is fretting, strings too low touching the frets;
front(forward) bow when strings are too high in the middle of the neck, usually fretting in the very end of the neck.
Is it same for you guys ?
in a couple of months I took it out and unclamped it and it was pretty darn straight. Mounted it back up and it was fine for a few weeks then the twist came back.
Wood need quite some time resting, before be used to craft a neck, specially a neck. It was probably made in a rush.
I would have waited 3-4 months or more depending on how much twist it had, @mresistor did you loose the rod sow to do it ?