It definitely doesn't mean we can stop vaccinating as that is only really an educated theory/guess of what herd immunity would be. It does however mean that like you say if take up dips a little we are still in good shape.
As we already know now the vaccine helps to cut transmission. Therefore the more people done the less likely any new variant will manage to take hold. So far all the new variants have actually only been similar mutations to previous ones. Which means are vaccinated should have a certain amount of immunity to even new variants.
The models are worst case scenarios really but still a good warning that we need to stick to are guns. Once restrictions are lifted more we will see for sure what is what🤷♀️