MacOS not booting with Clover timeout 0?

Hello! I'm experiencing a rather singular issue on my Hackintosh.

The machine I'm on consists of a Ryzen 7, a GTX 1070, a b450 MoBo and 16GB of DDR4 memory. I recently installed MacOS 10.13.6 (High Sierra), and everything seems to work great. I also have a few more partitions with some GNU/Linux distributions and Windows 10, so I'd rather use GRUB2 for its better Linux kernel flags handling.

I installed Clover on an EFI partition and I could easily get GRUB to chainload it, so now I have in my GRUB menu a "MacOS" entry that actually loads Clover, from which I can boot MacOS. I wanted to make Clover have a "0" timeout and automatically boot MacOS, without showing the selection screen, so that entering the "MacOS" option in GRUB would directly load MacOS itself (I'd still be able to invoke the UI by holding any key), but setting the config.plist accordingly leads to the infamous block sign screen, while setting the timeout value to -1 again (countdown disabled) boots correctly the OS. Of course I made sure to set correctly the default partition in the config.plist.

What could be causing this issue? Can it be solved, or troubleshoot in some way?