1-Open text_styles.tcw file
2-Go to Style Manager palette there are Text Style 1 - Text Style 4 with different text heights.
3-Save as this file to .dwg format.
4-Open that saved .DWG file.
5-Text style 1 and Text Style 4 both have different text height.

Solution:
To export the actual text height value of a text style, enable the "Set fixed text height for Text Style" option in the "DXF and DWG File Export" dialog (see the attached screenshot).