Well, they didn't find a need for it (assuming they would have under some circumstances), because there is nothing in the Hebrew version that suggests what is suggested in Matthew 1:23/LXX.
The part where it says "the deity gave (Qal) you a sign; Behold, a pregnant young woman is with a child..." the 'you" is a plural, there is no connotation to a virgin conceiving in the womb as the LXX says.
They also knew that the almah is not only used in two instances as Barnes claims, but in other parts of the Hebrew OT as well, especially in Prov 30:19-20, which dispell any notions of virginity or chastity.
The LXX drops the "maid" and makes the verses non sequitur.
Where did the "adulterous woman" come from?
So, there may be some truth in Paul Kahle's theory. However, that causes more problemns for the Christian side than for the Jewish side.
Verse 20 "such is the way of an adulterous woman" is certainly not something the writer would consider to be "too wonderful" for him. Verses 19 and 20 are parenthetical verses while verse 20 goes back to verse 17 ---