Yes God talked to Ahaz about his 'flesh' safety, and God told Ahaz about his 'spiritual' safety. Solomon wrote down about their being two bodies, the flesh under the sun and the spiritual body that returns to the Maker that sent it. And by what God told Ahaz is also instructional to us now even though it is history. Well at least most of that chapter is history.
You need to read ALL of Isaiah,Chap.7 to put Isaiah 7:14 into its’ proper context.
You cannot pick and choose from the Hebrew Scriptures.