Oh jeez. I understand that the OP is going to follow the parent's wishes on this, but this whole attitude of "how did my children survive" when grandparents are expected to adhere to new practices is just strange to me.
Were your children in car seats? Would you tell your son/daughter not to put your grandchild into a car seat now because, of course, they survived without one?
Babies born right now are born in a time where there is so much disease in the world, it is no wonder parents are cautious. Babies could catch Covid, RSV, Monkey Pox, Polio and now herpes from cold sores. They could die.
My own child spent 2 nights in the hospital at 2 months old with RSV because a relative who did not care about what viruses she brought with her when she visited. She thought, I just have a cold, no big deal. Until it wasn't.
Kissing a baby is not necessary and, IMO, expecting to kiss one or being upset about not kissing one is selfish. You are thinking only about what you want. You would feel horrible if, in the rare case, you transmitted anything too your grandchild and they ended up in the hospital fighting for their lives.