“Blank Lines” in this instance is not an “empty line”. It just means a completely empty string. Since the newline is a string, then no line is truly empty or blank. It always gives a correct count of the file lines.
I just created a file with 50 empty lines, and the 51st line says “The 51st line”. The result:

> find /c /v “” 51_lines.txt

———- 51_LINES.TXT: 51