No, they did not. What they meant was that already Delta is so contagious that only very limited amount of people can avoid it - r0 ~ 6-8 will make sure of it that ~85-90% of people must be immune to stop its spread.

Seasonal flu has r0 = 1.3. This means that it does not affect 75% of the population. The formula is p = 1 - (1/r0) to find out at what level of immunity the disease will die out.

Original Sars2 had r0 = 3, this meant that about 60% immunity level is needed. This is from where to original need of 70% of vaccinated comes from - vaccines do not give 100% immunity so you have to account for that.

Delta messed everything up. With p=85% and vaccine efficiency of 70% (because nobody, except Israelis dared to think about boosters first), you need more than 100% vaccinated - everyone gets is either vaccinated and lucky or vaccinated/unvaccinated and will get infected.