so why wouldnt a tuner be just as accurate for finding the first finger posistion on the G string?

a. you are ignoring the musical function (melodic, or harmonic) of the note.  In this context of a scale, pretty much everyone ignores the harmonic function because classical violin is taught from the perspective of a soloist, not an accompianment in a string quartet. 

b. dependency on the external source.  You are always trying to remember single notes in isolation and not in terms of intervals and musical function.  Therefore, you can't get away from the use of a tuner because memory just doesn't work that way.

d. tone quality as determined by the peculiarity of the string instrument.  You always want a ringing projected sound in the case of a classical soloist.  It sounds more pleasant...thats why in the case of playing A somewhere on the fingerboard you want the open string A to vibrate as much as possible.

Again, here is how my procedure works with regard to tuning the G-major scale.  The instrument (sympathetic vibrations) tells me where the A-natural goes.  The C-Natural is a perfect 4th from the open-G string.   The B-Natural is tuned high compared to the C-Natural above it.  The instrument tells me where the D and E naturals (again sympathetic vibrations) go.  The G-Natural is an octave above the open-G string.  And the F-sharp is tuned high compared to the G-Natural above it. 

So when I practice for the 1st time, I play just the notes that involve perfect intervals (4th, 5th, octave) with the open-G:  open-G, C (3rd finger), D (fourth finger), G (3rd finger).  This way I am thinking intervally rather than just playing single notes in isolation.  Then I would add leading notes, and so on, building the entire scale from scratch.

The way you guys do it, is just comparing to some thingy of which you have no understanding.  You try remembering sounds in isolation (tuner) or as an organic unity (drone sequence).  But memory doesn't work that way.  The same way those memory champions remember a deck of cards in sequence is not by trying hard, but an actual method which they employ.