Only the RSV calls it a young woman. All the rest say virgin.
Is 7:14 is quoted in Mat 1:23 and in all versions it says virgin.
First your assertion about how many translations use the term "young woman" is factually wrong. BBE, CEB, CJB, GNT, GNTA, NSR, NSRA, RSV, and RSVA, all use the term "Young Woman"
The word in Hebrew is הָ עַ לְ מָ ה (elome) which google translates as "damsel", a young unmarried woman.
בתולה is virgin, which is not used in the original Hebrew.
In addition, Jesus still wan't named Emanuel.