In fact this Russian use of a perfective future form with an imperfective
past meaning seems somewhat analogous to the Hebrew "vav conversive" idea,
although there is no equivalent of vav signalling it.
Waw conversive seems to me just that, conversive. This is another
controversial view.
I start by noting that Russian and English express imperative with one word,
and future - with two, with auxillary 'will.' That suggests later derivation
of future than of imperative.
The most common action is past. The first Hebrew verb form is past, qatal.
Consider conversive use of waw in hophal. Its use in weqatal was similar,
conversion into future tense.
Imagine command pronunciation of qatal. It would emphasize second vowel,
qatAal! That elongation reduces the first vowel, q'tAal! Elongated a tends
into o; consider Aramaic kamatz - Hebrew holam shift. Imperative thus became
q'tol!
ani qtol became iqtol (weak nun dropped); ata qtol became something like
taqtol. Someone got a bright idea of distilling affixes from pronouns.
tqtol, through the rule of two schwa in the word beginning, became tiqtol.
Imperative gave rise to the new form of future tense.
The yiqtol form was handy, and phased out weqatal which came to be reserved
for archaic narrations.
Asymmetry arose: two forms (weqatal and yiqtol) for relatively rare future
tense, one form for more common past. To balance the forms, waw-conversive
was similarly applied to yiqtol, making wtqtol.
Through the rule fo two schwa in word-beginning, schwa under waw became
patah. (Why not hirek? Perhaps, wi is unpleasant sound. Perhaps, hirek is
already used in pronominal prefixes, and two hireks in a row sound
unpleasant (witiqtol). Segholates show that hirek and patah equally appear
from first schwa. Another explanation seems more likely: wi or wa was a
diphthong ui or ua. With four vowels (uatiqtol), verbs had to have secondary
stress on diphthong. In accented environment, e becomes patah rather than
hirek. For this, consider nicnAsti vs. UaIrgish (hirgish). Diphthong in
yiqtol explains accent shift yiqtOl - UayIqtol).
The form wayiqtol was artificial and remained theoretical, employed to
impute sense of archaicity to narrations. In Russian, it was used similarly
(и скажет он).