Yocto use weston-init to start weston.
AGL add a bbappend on weston and do not use weston-init.

AGL should use the poky way to start weston.

Proposal:
1) use weston-init
In packagegroup-agl-core-graphics
use:
RDEPENDS_${PN} += "weston-init"
"
Instead of (Useless for AGL ?):
RDEPENDS_${PN} += "\
${@bb.utils.contains("DISTRO_FEATURES", "sysvinit", "weston-init", "", d)} \
"

2) remove weston service from weston recipes.
move fix on weston_%.bbapend to weston-init_%.bbapend