Here are a few magazine reviews of the final version of Shinobi III. Some of them state the game is too easy, but the screenshots they use prove they weren't playing it on any of the harder difficulty settings, as you can tell by how large the health gauge is.

Computer & Video Games
(Issue 142, October 1993)


Joypad
(Issue 23, September 1993)


Mega Tech
(Issue 21, September 1993)


Electronic Gaming Monthly
(Issue 23, September 1993)


MEGA
(Issue 13, October 1993)


SEGA official ad


SEGA Power
(Issue 46, September 1993)