That was actually feed back given from the US army to the development team at Heckler & Koch.
The rifle evolved form the kinetic energy carbine portion of the doomed XM29/OICW program, and eventually became the G36 rifle. In between those two, however, it was the XM-8, and it came close to adoption by the US military.The XM-8 was designed to be a very modular system, with a variety of interchangeable stocks, handguards, optics and accessories.
Video: [16:54] https://youtu.be/Te2IqFbRR7A?si=
https://www.forgottenweapons.com/hk-xm-8-what-was-it-and-why-with-larry-vickers/
https://www.forgottenweapons.com/almost-adopted-the-hk-xm8-family/
Is this where they took inspiration from for halo? Lol my first thought seeing this was the halo AR
The XM8 wasn’t designed until after Halo CE had been released, and it wasn’t really seen or known about by the public widely until 2003 at least.
If the Halo assault rifle drew from real life it may have taken some visual inspiration from the XM29 as a whole, the various versions of which had a much boxier and more industrial look. Mostly though, I think it is safe to say the Halo assault rifle is a riff on the Aliens pulse rifle. Very metal and industrial, and it even has the ammo counter and even a very shotgun pump looking handguard despite the Halo CE rifle not having a shotgun built in.
Although once people started noticing the XM8, it ended up in a ton of video games.