I suspect that when they say “other OS” they mean the likes of Windows NT descendants, Mac OSX descendants and Linux. Which are already fairly secure by design.
Haiku security, from what I gather, is perhaps more in a league with 1990s “multimedia computer” of the dial-up internet era OS such as Windows 9x and Classic Mac OS. So there would be a vast gulf between Haiku and modern commercial systems.
I read once that Microsoft and Apple essentially rebuilt their systems on top of 1970s era “minicomputer” systems to meet the safety requirements of full-time internet access. So Microsoft had Windows NT which was inspired by OpenVMS and Apple OSX which went for UNIX underpinnings.
In Haiku we talk of “glass elevator” which I take as a tacit admission that, to become truly mainstream, Haiku would need to be similarly recast to meet the standards of an always-online modern OS. Genode strikes me as a great foundation to build on. Haiku is in a position to leapfrog two generations at once and become equal to Google’s Fuchsia whose underlying “guts” were conceived this century.