I'm comparing the two e.g. on MyFonts:
https://www.myfonts.com/fonts/mti/helvetica-now/
https://www.myfonts.com/fonts/linotype/neue-haas-grotesk/
Or specifically for the medium text:
https://www.myfonts.com/fonts/mti/helvetica-now/text-medium/
https://www.myfonts.com/fonts/linotype/neue-haas-grotesk/pro...
Aside from the fact that they're scaled slightly differently, nothing whatsoever jumps out to me as noticeably different, in any weight, except that Neue Haas Grotesk has descenders that seem unnaturally short, but I can't tell if that might be a rendering box clipping issue.
What makes Helvetica Now "such a departure" and the name Helvetica just "marketing"? Whatever difference there is seems extremely subtle to my eyes...