I just caught myself doing this in a project I’m working on:

:root::view-transition-image-pair(*),
:root::view-transition-new(*),
:root::view-transition-old(*) {
  animation-delay: inherit;
}

I needed to do this to sync up the animation-delay from the ::view-transition-group(x) to its child-pseudos.

::root:view-transition-group(header) {
  animation-delay: 1s;
}

Without the first code snippet my animations were not in sync: the default fade-in/fade-out on the new/old pseudo ran at the wrong time.

I was surprised that animation-delay: inherit; on the pseudos isn’t part of the UA stylesheet VT styles, especially since the VT UA styles do exactly that for animation-duration (and animation-fill-mode):

/* UA Stylesheet (selection) */
:root::view-transition-group(*) {
  animation-duration: 0.25s;
}

:root::view-transition-image-pair(*) {
  animation-duration: inherit;
}

:root::view-transition-old(*),
:root::view-transition-new(*) {
  animation-duration: inherit;
}

I think it would be handy to include animation-delay: inherit for the -image-pair, -old, and -new pseudos in the UA stylesheet so that setting a delay on the -group automatically gets applied on the the child pseudos as well, keeping them all in sync.