It is for their target audience. They’re not talking to you, they’re talking to their customers.

I can still see parts of the desktop. They should really go all in and add some more blank space to the sides of the menu.

I’ve never used bcachefs so no help from me there.

/boot/efi is no longer considered an appropriate mount point

It’s not typical, but it should still work. systemd-boot even looks for the ESP there by default among /boot and /efi
Personally I use /efi.

just create a EFI partition and mount it /efi and let the OS put /boot inside the root partition if it needs it., then throw a UKI on /boot/efi/EFI/Linux

If I’m reading this correctly you mounted the ESP to /efi and then put the UKI in /boot/efi anyway. It needs to be on the ESP.
My /etc/mkinitcpio.d/linux.preset looks like this, if it helps. If you were to use /boot/efi for the ESP you would have to change the paths here.

# mkinitcpio preset file for the 'linux' package

#ALL_config="/etc/mkinitcpio.conf"
ALL_kver="/boot/vmlinuz-linux"

PRESETS=('default' 'fallback')

#default_config="/etc/mkinitcpio.conf"
#default_image="/boot/initramfs-linux.img"
default_uki="/efi/EFI/Linux/arch-linux.efi"
#default_options="--splash /usr/share/systemd/bootctl/splash-arch.bmp"

#fallback_config="/etc/mkinitcpio.conf"
#fallback_image="/boot/initramfs-linux-fallback.img"
fallback_uki="/efi/EFI/Linux/arch-linux-fallback.efi"
fallback_options="-S autodetect"

its possible that UKI, systemd-boot, bcachefs, and the /efi mountpoint are not a great mix

I don’t see the point of systemd-boot with UKIs. All it does is chain-load the EFI boot stub in the UKI anyway. I just used efibootmgr to create an entry in the UEFI which boots the UKI directly.