It's not. They both expose a POSIX API and userspace, but the underlying architecture is very different. macOS is in part based on the Mach microkernel, and creating a process has a bunch of work related to that.

Even ignoring that difference, macOS has built-in signature checking that suspends a newly-started process the first time its executable is seen.

Well…

If you want to run a desktop app you need to have it signed or jump through a few minor hoops to grant it permission. (Go to system settings, authenticate, allow it, then right-click and select “Open”)

But it’s not like it’s impossible.

Yeah, I remember when I tried to run an app on Linux, and it popped up and said: "Oops, the developer of this app you downloaded from the web hasn't paid $100/year ~~in protection money~~ for verification. Guess you'll have to navigate into your settings and allow running unverified apps for no reason which normal users with poor tech literacy will find burdensome or scary (and have to look up if and how they can do this, because the only options presented on the popup are 'Move to Trash' or 'Cancel')."

You don't have to defend Apple's obvious protection racket grift.

Damn, maybe some people don't know that none of this is hyperbole – or just really love denying reality and slurping down the dick of their favorite multitrillion-dollar corporation's OS. You cannot claim it's "just like Linux" when Apple steps in as a middleman to extort developers out of money. Below is what happens to your app when you don't pay Apple a ransom of $99/year (that's $100 for all intents and purposes, and I'm going to call it as much instead of playing along with the old-as-dirt '99' psychological trick).