oh god it's no different for current parents of young children.
Many of the baby items I bought for my first had been banned or recalled or advised against or had killed babies by the time I was babyshopping for no2.. and there wasn't even that big a gap between them!
The car seat I had for no1 had been exposed as unsafe and under tested.
I forward faced no1s car seat, now that I have no2 that's a no no until about 4years
I used cot positioners to keep no1 on their backs (kinda wedge things) to keep them safe, now they're dangerous and can kill babies
Peanuts were a no when weaning no 1, now they're a yes and its bad to introduce allergens to late if there's no family history…
We all had formula dispenser thingies and could add that to pre-boiled water when out and about with no1, by no2 they were a no, the formula had to be added when the water was 70 degrees to scald the powder..
It's not just nans. Mums of more than one have the same problem!