Sure the facility to fork still exists. So what? Observing that the kernel still provides fork() is like observing that the cpu still provides JMP.

It won't fork random processes you don't explicitly tell it to. I thought it was obvious that if you don't want unsolicited processes, then don't specify /bin/init as /bin/foo. The practical example is /bin/sh, but it could be any other executable.

Up to you to specify a binary that does what you want, and doesn't require a bunch of other processes like gdbus to function itself.

init=/bin/sh is more or less like ms-dos loading command.com

As much as DOS allowed multiple processes, even if only one was executed at the time and there was no multitasking outside of ill-fated MS-DOS 4.0 and various Concurrent DOS products.